The battle between Lewis Hamilton and Fernando Alonso will be more vicious than last year now they are in separate teams, says Red Bull's Mark Webber.
Hamilton and Alonso rejoin battle in separate camps this season
The Australian believes the restraints on their rivalry will be lifted after Alonso's move to Renault from McLaren.
"It could actually get nastier in terms of the battle on the track because the gloves are off," he said.
"Fernando can take the fight to Lewis - there is a bit of friction there. It could be fascinating."
Webber said it was unlikely Alonso's Renault team would be in a position to regularly challenge Hamilton's McLaren outfit and the Ferrari team of world champion Kimi Raikkonen.
But he said the Spanish double world champion will relish the chance to butt in on the fight between the big two teams on occasion.
Alonso left McLaren at the end of last season one year into a three-year contract because he fell out with the team.
"Fernando would love at the end of next year to have beaten both of them [McLaren and Hamilton] but he knows it's not possible in the first year," said Webber, who will be the BBC Sport website's F1 columnist this year.
"He's not saying he doesn't care about it; he's just being realistic.
"He's not stupid, Fernando, even though some things were a little wild last year. He's got his head screwed on.
Lewis is very good - but Kimi will probably win the title
"I think every now and then Alonso will put the cat among the pigeons.
"In the overall picture, he won't win the war, but some of the battles could get juicy."
Webber said he rated Hamilton's ability highly, but tipped Raikkonen to claim back-to-back titles this year.
"Lewis is very good," Webber said. "The car last year was very good but for him to operate at Fernando's level was exceptional.
"But Kimi will probably win the title. He and Ferrari have done very well in testing. He has probably worked out how to enjoy the sport more now he's won a championship.
"I don't think he's going to be around that long, so he's probably going to try to grab a few championships.
"He lost a championship at McLaren with an unreliable car, so to get it with Ferrari was very, very good for him, and I think Kimi can do it again."