Red Bull motorsport advisor Helmut Marko doubts Mark Webber has what it takes to cope with the intense pressures of a Formula 1 title fight.
In a revealing interview with Red Bull's in-house magazine the Red Bulletin, Marko has suggested that Webber is good enough to win a few races a year, but struggles to achieve a champion's consistency.
"It seems to me that Webber has on average two races per year where he is unbeatable, but he can't maintain this form throughout the year," said Marko.
"And as soon as his prospects start to look good in the world championship, he has a little trouble with the pressure that this creates.
"In comparison with Seb [Vettel's] rising form, it seems to me that Mark's form somehow flattens out.
"Then, if some technical mishap occurs, like with the alternator for example, he falls relatively easily into a downward spiral.
"No driver remains unaffected by this, because the tension is palpable.
"In 2010, it was particularly extreme. Webber headed into the final race with better chances than Vettel, and he probably carried the disappointment of his defeat into the 2011 season, which is so easy to understand."
Marko believes that Webber has struggled to cope with the psychological challenge of Vettel arriving just as Red Bull delivered the Australian his first title-worthy F1 car.
"Something that I think is also very important is that for much of his career, Mark was never in a top team, but he was always regarded as a high flyer if he only could get into the right team," added Marko.
"Then Red Bull puts him in a car - a possible winner – and suddenly along comes this young kid and he snatches the booty from under Mark's nose.
"Psychologically it's not easy, of course; this would gnaw away at anyone's confidence. It's more than understandable."
Webber won two races in 2012 – in Monaco and Britain – and finished sixth overall in the championship, having been Fernando Alonso closest rival at half-season.