Michael Schumacher to prove a point? (AFP)

Michael Schumacher takes his place on perhaps F1's most competitive starting grid after the former world champion came out of three years' retirement to race for the newly-formed Mercedes GP team, which bought out last year's constructors' champions Brawn GP.

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, among others.

"I love this fight - it is because of this fight that I came back to Formula One," Schumacher said.

Double Bahrain winner Alonso is one of the preseason favourites as the Spanish driver looks positively refreshed following his move to Ferrari, which also welcomes Felipe Massa back for the first time since he suffered a life-threatening crash at July's Hungarian GP.

"It's a very important moment for us after a horrible year. It was also a difficult moment for me with the accident. I'm concentrated, I'm ready 100 percent," said Massa, a double winner in Bahrain. "This is a fresh start for me. For all."

With the past two champions in its lineup the British McLaren team is also among the favourites, particularly after dominating three of the year's four pre-season test sessions. Button partners Hamilton and the former Brawn driver is savouring 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. "There are a number of teams and drivers who appear to be in the hunt, and, as with the start of every new season, it will be fascinating to see who emerges as the team to beat."

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.

Button's victory at Sakhir last year is the only non-Ferrari win at the Bahrain International circuit since its debut in 2004, when Schumacher won it.

Schumacher took over Button's seat as Mercedes' Silver Arrows returns to the track for the first time in 55 years with two German drivers at the helm. 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 tyres. Also, the top ten qualifiers on Saturday will not be able to swap tyres before the start, while the rest of the field can.

"You will have less sets of tyres available than last year which makes it harder to do what you need to do for setting up the car perfectly," said Schumacher, whose win here in 2004 is among his record 91. "But driving is always about adapting to new circumstance, and this is one of my strong points."

Fellow German driver 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 are one of only three teams whose drivers lineup has not been altered in the 12-team, 24-car field, along with Toro Rosso and Force India.

Williams, Force India and Sauber are also expected to be in the points and have even been tipped to surprise at a track that has been changed to 49 laps instead of the usual 57. The desert track features a new, longer configuration with eight additional corners making it the second longest race on the 19-track series after Spa.

"We will have good racing there, I think, and all I want is to fight because this is what I missed most," Sauber driver Pedro De la Rosa said as the Spaniard takes the grid for the first time since 2006.

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, Virgin Racing and Hispania Racing Team also mark their debuts. HRT-F1 was the only team not to test and only named Karun Chandhok to partner Bruno Senna last week. Senna is the nephew of triple champion Ayrton Senna.

Several of the leading teams have criticised the decision to allow in so many new teams, especially as they are well off the pace.

"I am under no illusions about what we're in for," Chandhok said. "At the end of the day, we will be a new team with two rookies and no testing at all, so the first few races will be very hard indeed. If we can finish the first race that would be an achievement."