Week 4 of the NFL season sort of marks a line in the sand.
By the time Monday night's game ends, for the most part, we'll have a pretty good idea which teams are poised to compete for playoff spots and which are down for the count.
That's not to say that any 3-1 team will stay competitive or that a 1-3 squad's done, but history's taught us that this is about the time in the season where things start sorting themselves out.
So, who's going to step up on the first Sunday of October? What games are worth keeping an eye on? Here's a look:
• Surprising showdown in Big D
Could Sunday's Lions-Cowboys game be a playoff preview? Ok, Ok, we're getting ahead of ourselves, but Detroit has been one of the biggest stories of the NFL season thus far, sprinting out to a 3-0 start.
Dallas -- and more specifically, Tony Romo -- has gotten its fair share of love, too. Romo's led back-to-back come-from-behind wins, including a dramatic 18-16 victory over Washington last Monday night. The Cowboys' gunslinger pulled off that one despite a depleted receiving corps and a center who couldn't learn the snap count.
The banged-up Cowboys have a bye after this one, so getting to 3-1 with the chance to rest could set them up for a big rest of the season. But the thought of the Lions improving to 4-0 with three road wins is pretty remarkable.
• Will Chris Johnson finally step up?
This certainly is not what the Titans had in mind when they gave their star running back a huge contract extension at the end of the preseason. Johnson has yet to get to 100 yards rushing on the season, a 34-yard reception in Week 3 is the only thing keeping him from being a total non-factor this season.
The fact that Tennessee is 2-1 in spite of Johnson's struggles should give the Titans hope for the rest of the season. They'd still feel better if Johnson could do some damage in Cleveland Sunday.
• Michael Vick health watch continues
Vick left the Eagles' Week 2 game in Atlanta with a concussion, and Philadelphia went on to blow a lead and lose. In Week 3, Vick injured his hand after taking a hard hit, and backup Mike Kafka threw a crushing interception late in a loss to the Giants.
Plain and simple, the Eagles need Vick to stay healthy. He's supposed to play Sunday against the 2-1 and NFC West-lead 49ers, a game that Philadelphia should win at home.
A third straight week with Vick stumbling to the sideline, though, and the Eagles will have to be genuinely concerned about their season.
• Texans get another chance for a signature win
Houston let one slip away in Week 3, crumbling in the fourth quarter against the Saints. For a team that's had trouble getting to the playoffs, the Texans definitely could have used a huge confidence-inspiring victory over an elite NFL team.
Big picture, this could also wind up being a huge game in the AFC playoff race. The Texans and Steelers both have their sights set on their respective division titles. But the AFC postseason picture figures to be cloudy all year, which means that games pitting contenders carry a bit more importance.
• St. Louis' last stand?
Nothing has gone right for the Rams in 2011. They've lost their first three games, while scoring just 36 total points, and have been hammered with key injuries.
Even in the shaky NFC West, falling to 0-4 would put St. Louis in an almost-insurmountable hole -- especially given the Rams' next three games after a Week 5 bye are against Green Bay, Dallas and New Orleans.
All of that makes Sunday's game against the Redskins a virtual must-win for the reeling Rams.
Their paths haven't been exactly the same, but both the Vikings and Chiefs enter Sunday's game in Kansas City at 0-3. Minnesota has gotten there by coughing up second-half lead after second-half lead; Kansas City has been outscored by 82 points -- and that's including a close Week 3 loss in San Diego.
Is there any life left in either of these teams? This one's a challenge of pride for two reeling teams. We'll have to see if either responds.
Meanwhile, on the opposite end of the AFC West spectrum from the Chiefs, the upstart Raiders are 2-1 and could be 3-0, if not for a late collapse in Buffalo. Oakland is still tied for first place in the division and looks more and more like a possible playoff contender each week.
The next test comes Sunday, as New England visits the Black Hole, one week after the Patriots suffered a shocking loss to the Bills. Tom Brady's crew figures to be angry, but the Raiders would love to energize their rejuvenated fan base with a huge home win.
• Rex Ryan's return to Baltimore
Monday night's Colts-Bucs game (we'll get there) could be a snoozer, but the Sunday nighter -- the Jets at Baltimore -- has the feel of a special one.
New York sits at 2-1 and a little battered after losing in Oakland last week. Baltimore, meanwhile, shook off a lethargic Week 2 loss to smoke the Rams in St. Louis last Sunday.
Both teams feature outstanding defenses, up-and-coming quarterbacks and their fair share of brash personalities. Oh yeah, and Jets coach Ryan used to call the plays for that feared Ravens defense. He's sure to bring a little extra gusto to the table this weekend.
• Colts' quarterback controversy
Curtis Painter took over for an injured Kerry Collins late in Week 3. The results were mixed -- Painter coughed up a fumble that resulted in a Pittsburgh touchdown, but also led a late scoring drive against the vaunted Steelers' defense.