World champion Sebastian Vettel on Saturday admitted he needs to up his game.
The German has won the last four drivers' titles on the trot, but all of them were alongside Mark Webber, who retired at the end of last season.
Australian Webber was replaced at Red Bull by his compatriot Daniel Ricciardo, who so far in 2014 has outqualified Vettel on no fewer than three out of four attempts.
Told that Ricciardo is clearly more competitive than Webber, Vettel said after qualifying in China: "Well, that's (not) a compliment to Mark, I should say, in his absence.
"I think this year is very, very different, the cars are very different so I don't think you can compare last year to this year," he insisted.
"But nevertheless, I think Daniel is doing a very good job, he has not just had one good weekend, he had good weekends and so far he seems to be able to get the maximum out of the car," Vettel admitted.
"On my side, maybe I'm struggling a little bit more, but at the end of the day we have the same car -- there's nothing between cars, so if he manages to beat me, then he beats me on the circuit, fair and square," he said.
"Of course, that's not to my liking but equally, I know that I have to do a little bit better."