Storylines and matches to watch on Day 4 of the Australian Open (click here for the order of play):
• Serena Williams does double duty: Forty-eight hours after rolling her right ankle in her first-round victory, Williams will start her day against a young Spaniard, Garbine Muguruza (second match, Rod Laver Arena), before playing doubles with her sister Venus in the afternoon. The obvious intrigue is Serena's health. The five-time Australian Open champion practiced Wednesday in a closed session, avoiding the prying eyes of fans and reporters who wanted to assess her movement. USA Today's Doug Robson, one of the few who was invited to the private workout, reports that she was moving relatively well.
If there were serious concerns about that ankle, I suspect that Serena and Venus would have withdrawn from doubles by now. All signs point to go.
• The new era of Andy Murray: It's remarkably refreshing to be in the first week of a Slam and not have the conversation dominated by the "Will Andy Murray finally break through" punditry. If it's refreshing to me, it must feel like the Twilight Zone for Murray, whose interviews are now focused on the positive rather than the negative. Murray's first-week matches used to be must-see events, mostly fueled by the cruel desire to be there when yet another Slam campaigned failed. Now there's an expectation, much like there is for Novak Djokovic, Roger Federer and Rafael Nadal, that these early matches are simply tune-ups and the opposition won't offer too much resistance. That's quite the sea change for Murray. He cruised in his first round and he'll take on Portugal's Joao Sousa (second match, Hisense Arena) on Thursday.
• Can U.S. women keep it going?: Serena Williams, Sloane Stephens, Varvara Lepchenko, and Jamie Hampton will try to join Venus Williams and Madison Keys in the third round. If all four win, the United States would have six women in the third round of a major for the first time since 2005. Serena, of course, is a heavy favorite against Muguruza, while Stephens, Lepchenko and Hampton all have winnable matches. Stephens will take on a fellow 19-year-old in 97th-ranked Kristina Mladenovic, and Hampton will face 19-year-old Thai qualifier Luksika Kumkhum. Lepchenko has the toughest test, against Russian veteran Elena Vesnina, who won in Hobart last week for her first WTA title.
Matches to watch
• No. 2 Roger Federer vs. Nikolay Davydenko (first night match, Rod Laver Arena): This throwback match has two 31-year-olds meeting for the 20th time. Davydenko is only 2-17 against Federer, but the Russian's resurgent early-season form -- he upset David Ferrer 6-2, 6-3 in the Doha semifinals two weeks ago and lost a tight final to Richard Gasquet -- raises hopes that this might be a competitive match. Three years ago, Davydenko was up a set and a break against Federer in the Australian Open quarterfinals before fading in a four-set loss. Federer, playing his first tournament of the year, looked sharp in his first-round victory against Benoit Paire.
• No. 8 Petra Kvitova vs. Laura Robson (second night match, Rod Laver Arena): This is the pick-'em match of the day, as the two hard-hitting lefties meet for the first time. Kvitova caught a break in being scheduled for a night match on a day that's forecast to be the hottest of the week, eliminating the possibility that she might wilt in the heat. Robson's game has been compared to Kvitova's, both in her power and shotmaking as well as her penchant for in-match walkabouts. The Czech struggled through her first-round win over Francesca Schiavone, while Robson cruised past Melanie Oudin. At their best, Kvitova is still the better player right now, but it's been a long time since we've seen her at her best. Robson is a big-match player who loves the show courts, and the Aussie crowd will be backing the Melbourne-born teen.
• Daniel Brands vs. Bernard Tomic (third match, Rod Laver Arena): Can Tomic continue his 2013 unbeaten streak (9-0, including the Hopman Cup exhibition) to set up a potential third-round clash against Federer? He should get through against No. 120 Brands, though the German had a great season-opening tournament in Doha, making the semifinals as a qualifier.
• No. 21 Varvara Lepchenko vs. Elena Vesnina (first match, Court 2): This is a tricky matchup for Lepchenko, who is seeking her fourth consecutive third-round appearance at a Slam.
• No. 13 Milos Raonic vs. Lukas Rosol (second match, Court 13): Hey, look, Lukas Rosol! We have to keep an eye on that guy. Who knows when lightning will strike twice. • Upset specials: Laura Robson over Petra Kvitova; Jeremy Chardy over No. 30 Marcel Granollers (third match, Court 8).