Lewis Hamilton has named his old McLaren team-mate Fernando Alonso as the man he most wants to beat in 2013.
The 2008 champion says the Ferrari driver - second to Red Bull's Sebastian Vettel in 2012 - will be his benchmark as he begins his Mercedes career.
"Alonso's the fastest driver I can see," said Hamilton, whose team-mate Nico Rosberg was quickest in testing.
"I think Ferrari are going to be quick this year. He's the guy I want to beat. Anyone would struggle to beat him."
Hamilton made a stunning debut as Alonso's team-mate in 2007 before their relationship turned sour over which of them was the team's de facto number one.
Alonso left to rejoin Renault - with whom he won the 2005 and 2006 world titles - but he and Hamilton now share a mutual respect.
The Spaniard nominated Hamilton as the strongest driver on the grid in the build-up to the new season.
Hamilton said renewing his rivalry with another former team-mate Jenson Button did not interest him.
"The rivalry between me and Fernando excites me more," added Hamilton. "Trying to finish ahead of Alonso, in a Ferrari that is actually really competitive, is a really nice challenge.
"You also want to beat Seb [Vettel] as they are the ones with most titles."
Hamilton knows how it feels to be the driver everyone is aiming to beat and it is a position he hopes to get back into with his new team.
Mercedes set the fastest time in winter testing and, although Hamilton played down his chances, Mercedes appear to have made a step forward.
"We all want to be the one," he said. "I was the one for a short period of time.
"Now it's toppled over to Sebastian. But I want to be at the forefront. People see [seven times champion] Michael Schumacher as a god and that's where I want to be."