AUSTIN, Texas -- Sebastian Vettel says Ferrari's resurgence at the U.S. Grand Prix came as too little too late as he heads to the next round in Mexico expecting to be eliminated from the title race.

Vettel's teammate Kimi Raikkonen won Sunday's race in Austin, but Vettel could only manage fourth place after a grid penalty and first lap spin left him needing another comeback drive. It was Ferrari's first win since the Belgian Grand Prix in August and came after the team removed a series of updates added to the car at the last three rounds.

The return to form could be seen as a positive for Ferrari, but Vettel was left frustrated that it has taken three races for the performance to improve.

"It took too long," he said. "You can see it as good news but you can also see it as bad news.

"If we have to go back to a car that has been competitive three or four months ago, surely it can't be good news if you think about it."

Vettel has won one race since the summer break, at Spa, in late August. Clive Mason/Getty Images

Vettel admitted the team still doesn't fully understand why it struggled so much at recent races.

"It's a bit hard to explain," he added. "If you don't see that there is a problem, you don't think that there is a problem. We felt the car was not as strong as it was before but if you don't see there is anything wrong then you don't know that there is something wrong.

"All the steps we did, they seemed to make sense. But now looking back, they didn't. Clearly there was something missed. We haven't understood why and where the aero took off and started, there is a lot of stuff for us to do and understand, but I'm pretty sure we will do what is necessary and get on top of it."

In order to stage a dramatic turnaround in the championship, Vettel must win all three remaining races and hope Hamilton scores less than five points over the same period. Asked about his championship chances he said: "They are getting slimmer, but we will try to head to Mexico and get the best out of our car. Maybe there are some elements we can improve.

"Probably the last four or five races, we haven't done so well. Obviously the last couple of months haven't been good for us, in many regards.

"We had another recovery drive today, but I'm getting a bit tired for recovery drives. It's fun to race but I'm pretty sure at that some point the coin might flip to the other side."