Hitting a baseball or golf ball (in a straight line) are often cited as the most difficult things to do in sports, but it seemed to us that plenty of people on the planet can do them -- even well enough to be successful in the major leagues or as professional golfers. Likewise for returning a tennis serve, finishing a triathlon, competing in a downhill ski event or myriad other activities..

So when it came time to ponder ultimate difficulty, we tried to pick things that even elite athletes in a variety of sports find almost impossible to achieve. Ranking these 10 feats by degree of difficulty ultimately proved impossible, for obvious reasons.

"Every sport has its own particular skill set that is required at a high level," says hockey legend Mark Messier. "Hockey is very tough because you have to match two skills. One is the stick skills and two is obviously the skating. There's only one other sport where you have to do that and that's polo -- riding the horse and mastering the mallet. I have to give hockey players a lot of credit because there is lot to mastering both those skills. I also think stopping a penalty shot is tough. Fortunately, I've never had to do that, but I've blocked a few shots... reluctantly (laughs)."

So here are our 10, in no particular order, accompanied by the thoughts of a notable expert on each sport. Agree? Disagree? Have something you think belongs? Weigh in here.

Last to do it: Ted Williams (.406, 1941) Why it's so hard: "I don't think anybody's going to do it," says Braves third baseman Chipper Jones. "It was easier when you had starters going 300-350 innings. You could plan on seeing a guy 4-5 times during the course of a game and make your adjustments. Now, you're probably only going to see a pitcher for two or three at-bats. Then you've got the specialty pitchers. Most people bring in lefty specialists, who turn me around [to bat righty]. Then I get the closer in the ninth. So, by no means do I think I'm gonna be the guy. Ichiro [Suzuki], who gets 60 to 75 infield hits a year because of his legs and has the ability to get well over 200 hits in a season, might be able to do it. He shrinks the field on you because he is so fast. And once you field the ball cleanly, you still got to bust it to make the throw. It would be a guy like him, with his kind of game. But then again, I don't know if he walks enough. When he goes 0-for, he goes 0-for-4 or 0-for-5, whereas I go 0-for-2 or 0-for-3. The simple fact of the matter is nobody has done it in a very, very long time. And you're talking about maybe the greatest hitter that ever stepped on the field who did it last." -- as told to John Donovan

SI VAULT: Farewell, Teddy Ballgame (07.15.02)

Last to do it: Bruce Bowen ... for awhile Why it's so hard: "He's so precise with his moves," says Spurs forward Robert Horry, who has won seven NBA championships, including three with the Lakers from 2000-02. "A lot of guys are wild, but he takes the right angles and uses them to the best of his ability. The thing about it is he has a great shot fake, so you don't know when to stay down, and if you do stay down, he jumps over you. If you don't stay down, he can get up on you and get a foul called. He has a variety of aspects in his game that makes him so effective. I call it the efficiency of movement. He's cut down a lot on just running around and calling for the ball. He's saving his energy for the right moments. He's not overextending himself. His talent has always been there -- he probably should have won the MVP two years ago when he scored 81 points in a game -- but now the people around him have gotten better and when the people around you get better, you have a lot more confidence in those guys. He's using them more, so now you don't know if he's going to shoot or pass." -- as told to Arash Markazi

SI VAULT: Kobe's Killer Instinct (06.02.08)

Last to do it: Johnny Vander Meer, June 5-11, 1938 Why it's so hard: "The reason why it is nearly impossible is there's no rhyme nor reason to the game of baseball," says YES broadcaster Al Leiter, who won 162 games over 19 seasons and threw a no-hitter against the Colorado Rockies on May 11, 1996 as a Florida Marlin. "You can have an impeccable game plan and fantastic routine and it doesn't matter: You can be perfect in your execution and still give up a hit. I gave up a hit pretty early in the next game [after my no-hitter] and the irony is I am certain it was a swinging bunt or a huge swing that rolled in front of the third baseman. I think in other sports if a play is done right with players who are prepared properly, you will see results more times than not. In baseball, no. How many times do you watch a game where there's a 2-0 fastball right down the middle to a guy getting paid a lot of money and he pops it up or misses it? Or you throw an unbelievable slider three inches off the ground and Vladimir Guerrero hits a double to right-center? They say Joe DiMaggio's hitting streak is the hardest streak in any sport, but I would argue that throwing back-to-back no-hitters is harder. As a pitcher you are so left out there for uncertainty. As a hitter, you are in control with your execution. How many years have we played baseball? Multiply that by how many games we've played and once upon a time a guy threw back to back no-hitters." -- as told to Richard Deitsch

SI VAULT: Bright Night in Brooklyn (08.07.63)

Last to do it: New England Patriots (2004, 2005) Why it's so hard: "First of all, it was hard before the salary cap, too," says CBS NFL Insider Charley Casserly, who served as GM of the Washington Redskins and Houston Texans during his 24-years as an NFL executive. "The difference now is the continuity factor. In this system, it's hard to have quality depth because players who are good at the end of four years, you either have to sign for a lot of money or you lose them. At a couple of positions, you might have some veteran players, but then you have other positions where you will be backed up by rookies. When you have injuries, you are not going to be as strong. Plus, the schedules are pretty balanced and two games will be affected by your record the previous year. You don't have the super teams anymore, but the tradeoff is great balance in the league and therefore the teams that win the Super Bowl are really winning more of a tournament. A play here or there can knock you out of the playoffs. Now, if you want another of the toughest things in the NFL, how about Don Shula's coaching career victory record (347)? I'm not sure anyone will get remotely close because he started so young and he was great." -- as told to Richard Deitsch

SI VAULT: One Really Sick Performance (02.16.05)

Last to do it: Yelena Isinbayeva (16-5 ¼ indoors in 2005) Why it's so hard: "Pole vaulting is a very unnatural act," says Jenn Stuczynski, the holder of the American women's record of 16 feet 3/4 inches. (The only woman who has jumped higher is Isinbayeva, the defending Olympic champion). "To run full speed into something is not something you typically do. And this is a sport where you have to run full speed toward something while carrying a pole. A lot of people don't know that pole is made to bend only one way. It's kind of like golf where you have a sweet spot on the club. So it's something very technical, and then you have to invert your body upside down. To go upside down over a box is scary, and you get scared because there are a lot of things that can happen. It's a dangerous event and to watch it live is different than television. People see it and tell me, 'I can't believe someone can do that.' I can tell you that once you are in the air, motor patterns take over. It may seem like the pole vault takes long time, but it's very fast. There's no time to think, like in golf." -- as told to Richard Deitsch

SI VAULT: Soaring Ambitions (03.08.99)

Last to do it: Brett Hull (86), St. Louis Blues, 1990-91 Why it's so hard: "The goalies are way better - that's the biggest reason why it doesn't happen anymore," says Steve Yzerman, the legendary former captain and current vice president of the Detroit Red Wings, who scored his career-high 65 in 1988-89, the same season that Mario Lemieux of the Pittsburgh Penguins lit the lamp 85 times. (Wayne Gretzky -- 87, 92 -- is the only other member of the 80-plus club.) "You don't get as many easy ones like you used to coming down the wing, slap shots going right through the goalie's legs. But yeah, I do [think we'll see it happen again.] It may not be next year, but if you look at forwards' ice time now, these guys are playing 24, 25 minutes (per game) because teams simply aren't going to have the depth (due to the salary cap). For a while, these guys were at 17 to 20. What did Alex Ovechkin score this year [66 goals]? With a couple more years under [Capitals teammate] Mike Green's belt, Nicklas Backstrom's belt, Alexander Semin's, I think [Ovechkin] might get there. I don't know about 80, but you'll get into the 70s again for sure in the next three or four years. Those [Washington] guys are going to be tremendous." -- as told to Michael Farber

SI VAULT: Shooting Star (03.18.91)

Last to do it: Bobby Jones, 1930 Why it's so hard: "Four different golf courses, four different playing conditions spread out over five months," says Nick Price, winner of three major championships (two PGAs, one British Open). "The thing about golf is, you can get into a good run for six or seven weeks. But to extend that for five months, there have been very few golfers who have the ability to tweak their games before the majors. Jack Nicklaus was probably the best before Tiger Woods came along, although that's still debatable. You've got cruel windy conditions and fast greens at the Masters, then heavy rough and hard greens at the U.S. Open. The British Open is all about bouncing the ball onto the greens and using some creativity. Then you go to the PGA in August and it's hot and the greens are a little softer. All four are very different. The hardest thing is to keep that momentum going from April through August. Even when I played well for a period of four and a half years, I was still streaky within that time. I'd play well for two months, go off a little, then pick it back up again. Tiger is one of the three guys who ever played the game who could probably win the Grand Slam. He had all four trophies at one time, but I don't think any other human being will ever do that. There was so much pressure on him this year because everyone was talking about the Slam. You could see there was tension in him during that first round at the Masters. For anybody else to do it, they'd have to beat Tiger four times and that's another big challenge." -- as told to Gary Van Sickle

SI VAULT: The Silver Anniversary (09.12.55)

Last to do it: Miki Ando (2002 ISU Junior Grand Prix Final) Why it's so hard: "Miki Ando (the 2007 world champion) is the only one who has it in her arsenal and has actually done it in front of a panel of judges," says NBC figure skating commentator Scott Hamilton, the 1984 Olympic gold medalist and four-time world champ. "I think a lot of it is the physical changes when a woman's body matures. The way she would be able to rotate a jump changes. For a quad, it's so tough to spin one of those jumps and stay in the air long enough to complete the rotations. You see what a 14- or 15-year-old girl can do with jumps, but when they get to 17, 18 or 19, their bodies and centers of balance change enough where it's tougher to pull out of those rotations. When you look at the women's sport, how many triple-axels have been landed in competition? You have Kimmie Meissner, Tonya Harding, and Midori Ito. There are not a lot of people completing the triple-axel. They do the other triples consistently, but the triple-axel is really the next milestone. The quad is really rare and probably a long way off. I went four years without losing a competition. I won an Olympic gold medal and world championships and never even attempted a quad (laughs). Hey, I'm not crazy. I knew which way I wanted my feet to point when I was 50 years old." -- as told to Richard Deitsch

SI VAULT: Flash of the Future (01.24.05)

Last to do it: David Robinson (34 points, 10 rebounds, 10 assists, 10 blocks) for San Antonio vs. Detroit on Feb. 17, 1994 Why it's so hard: "Quadruple-double?" asks Lakers forward Luke Walton, who averaged 7.2 points, 3.9 rebounds and 2.9 assists this season. "What's the fourth one? Blocks? Steals? Yeah, that's hard right there. It's really hard to get a triple-double. You have to be a player who plays the majority of minutes and you have to be versatile because there are a lot of shooters in this league. You have to pass, shoot and rebound, and to get to the quadruple-double you've also got to be a shot-blocker or get a lot of steals. It's hard because you can kind of control points and rebounds, but to get 10 or more assists in a game is hard, and 10 or more blocks or steals is something else. Wow, that's rare." -- as told to Arash Markazi

SI VAULT: Spur of the Moment (03.07.94)

Last to do it: Don Gay, (1974-77,79-81, 84) Why it's so hard: "I think just staying on a bull for eight seconds is the hardest thing in my sport," says two-time champion Justin McBride, 28, the holder of the Pro Bull Riders' elite circuit records for career wins (30), events won in a single season (eight) and career earnings ($4.9 million). "You've got to do your basic things right every time to have any chance. It's like hitting a tee shot or taking a three-step drop as a quarterback, but you're not competing against other humans, you're competing against a 2,000-pound animal, and that makes it tough mentally as well as physically. Winning three [PBR] championships like Adriano Moraes has pretty much been the milestone. It's attainable, and four is a possibility, but you've got to get the first one at a young age. You're not going to do it if you win your first when you're 30. We've got some young guys like Guilherme Marchi (25) -- he's going to be the champion this year -- who have a shot to win four. Donnie Gay won eight (Pro Rodeo Cowboy Association world titles before PBR was founded in 1992) and I don't think you'll see anyone do that again. It's not physically possible with the bulls we have today. We'll be lucky to see guys have eight- or nine-year careers because our season is such a grind (34 events). You're getting on 100 bulls a year, week in and week out. The toughest bulls there are, and injuries are such a part of the sport. I've ridden with a rod in my hand. I broke both bones in my leg and had 11 screws put in and rode three weeks later. I put my shoulder surgery off until after the World Finals last year and was riding with it taped. I don't plan on riding more than another five years." -- as told to John Rolfe

SI VAULT: No Guts, No Glory (09.06.82)

Start 275 consecutive games in the NFL (Brett Favre); Throw a touchdown pass in 47 consecutive games (John Unitas); Win horse racing's Triple Crown as a jockey (Steve Cauthen); Win both ends of Double Duty (Indy 500/NASCAR's Coca-Cola 600 on the same day -- yet to be done); Win seven consecutive Tours de France (Lance Armstrong, 1999-2005); Win dogsled racing's Iditarod and Yukon Quest back-to-back two years in a row (Lance Mackey); Watch ESPN's Around The Horn.

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