Former Formula One driver David Coulthard has hit out over Sebastian Vettel's attitude over recent weeks, suggesting the German is unhappy at Ferrari.

Four-time world champion Vettel looks set to miss out to Lewis Hamilton for the world championship again, with the Brit within touching distance of sealing his fifth title.

Though Vettel and Ferrari made a good start to the season by winning the first two races, they have not been able to match the consistency of Hamilton and Mercedes, who went on a four-race winning streak between Italy and Japan in recent months.

And though Ferrari ended that dominant spell in Austin at Sunday's US Grand Prix, it was Vettel's teammate Kimi Raikkonen that secured victory, with the German's title hopes continuing to slip away.

In a season littered with individual mistakes for Vettel, he yet again made life hard for himself in Texas by spinning his car on the first lap after a collision with Red Bull's Daniel Ricciardo.

Though Vettel still recovered to finish fourth, Hamilton's third place means that he will be confident of finishing the title race in Mexico.

Vettel has now hit a Red Bull car twice in the last two races, and there's no doubt that he enjoyed his spell with them much more than his current one with Ferrari, with all four of his titles coming with the Austrian team.

And pundit Coulthard has launched a scathing attack about the amount of time Vettel has been spending with his previous employers in recent weeks.

After having to play catch up in a race that he could have won in the US, Vettel said he is "tired" of having to pull off recovery drives. Coulthard however, says his problems may come from deeper concerns with his team.

During Channel 4's coverage of the Grand Prix, Coulthard stated: "He's a four-time world champion, he's made two mistakes in two corners, one mistake you can say you're finding where the car is…

"He says he's tired - when you're tired you go for your comfort blanket. I've seen him around Red Bull more often in the last few races than at any other time that he's been at Ferrari.

"So he's not knuckling down with his comfort blanket at Ferrari. To me it looks like he's not only tired of the recovery drives, he's just not as happy within the team as he was at Red Bull."

Vettel left Red Bull after a dominant stint as he sensed that Ferrari were about to produce a more competitive package, but will he ever win a title with them whilst Mercedes can provide Hamilton with such strong cars?

Despite often promising much over the last couple of seasons, Ferrari have not been able to go the distance with Mercedes and yet again see their title aspirations in tatters. No wonder he's starting to wander around the paddock.