MADRID — Months of anticipation and speculation finally will come to a close Sunday when the 2010 Formula One season gets under way and Michael Schumacher marks his return to racing at the Bahrain Grand Prix.

The seven-time F1 champion headlines perhaps F1’s most competitive starting grid, coming out of three years of retirement to race for the newly formed Mercedes GP, which bought out last year’s constructors’ champion Brawn GP.

The 41-year-old Schumacher said he felt like “a child at Christmas” coming to Bahrain, where he’ll line up against defending champion Jenson Button, two-time champion Fernando Alonso, 2008 winner Lewis Hamilton and talented Red Bull driver Sebastian Vettel.

“I love this fight,” Schumacher said. “It is because of this fight that I came back to Formula One.”

Two-time Bahrain champion Alonso and Ferrari are the preseason favorites as the Spanish driver looks reinvigorated following his move to the Italian team, which also welcomes Felipe Massa back for the first time since he sustained life-threatening injuries in a crash at the Hungarian GP in July.

Massa said McLaren’s design was “strange,” but with the past two champions in its lineup the British team is among the favorites. Button partners Hamilton, and the former Brawn driver is savoring the No. 1 tag on his car.

“It’s a responsibility and an honour, but it’s something I’m going to enjoy for as long as I can. I don’t want to lose that number from my car,” Button said.

McLaren’s rear wing is under scrutiny after Red Bull expressed doubts over its design, with the British team confident it conforms to regulations and governing body FIA set to check it at Friday’s opening practice.

Schumacher took over Button’s seat as Mercedes’ Silver Arrows return to the track for the first time in 55 years. Fellow German Nico Rosberg also makes his Mercedes debut.

Schumacher’s experience could pay dividends as refueling is now banned, meaning teams will only pit to change tires. Also, the top-10 qualifiers on Saturday will not be able to swap tires before the start on Sunday, while the rest of the field can.

Fellow German Vettel will be looking to make a mark as Red Bull is expected to be in the title mix a year after it was Brawn’s closest challenger.

“You can’t underestimate the opposition, but expectations are high at Red Bull now,” team principal Christian Horner said. “We just want to get the most we can out of every weekend.”

Vettel and teammate Mark Webber make Red Bull one of three teams with the same drivers as last year. Toro Rosso and Force India are the others.

Williams, Force India and Sauber are also expected to be in the points and have even been tabbed to surprise at a track that has been changed to 49 laps instead of the usual 57. The desert layout features a new, longer configuration with eight additional corners making it the second longest race on the 19-track circuit after Spa in Belgium. Renault, meanwhile, is hoping just to reach the final qualifying session with Robert Kubica leading the French team.

Three new teams will be on the track as Malaysian-backed Lotus returns for the first time since 1994, while Virgin Racing and Hispania Racing Team also will debut in the 12-team, 24-car field. HRT-F1 was the only team not to test and only announced last week that Karun Chandhok would partner Bruno Senna, the nephew of three-time champion Ayrton Senna.