Mark Webber has tipped his last F1 teammate Sebastian Vettel to eventually return to the top of the sport.
Dr Helmut Marko, the world champion team's outspoken director, has admitted to the BBC that amid Vettel's personal struggle earlier this year, he told the 26-year-old to "raise his game".
"Sebastian was complaining about having such a bad car," the Austrian said. "Furthermore, he thinks the way F1 is going is not the right one -– the cars should be monsters, not relatively easy to drive.
"With all these problems, maybe he wasn't as committed as he should have been, but that has changed," added Marko.
Webber, who had a competitive return to Le Mans at the weekend until his Porsche prototype retired, told motorline.cc that Vettel has also had a "hard time" in 2014 with "many technical problems".
"But I am not surprised about Daniel," he said. "I said before Melbourne that he would be 50:50 with Seb and everyone said I was crazy, but Seb will be there again -- he just needs some time to deal with the car."
Webber said Ricciardo is clearly a top F1 driver, but whether he is as good as the highly-successful Vettel is a question yet to be answered.
"For Seb, it's difficult at the moment because Mercedes are the absolute favourites," he said.
"But as soon as Seb sees victories again, he will be back. It's the same with Fernando (Alonso). When he sees an opportunity to get the win, he is always there.
"In the first half of this season, the fact that only Mercedes could win was easier for Daniel to accept," Webber added.
Speaking separately to Fairfax Media, Webber continued: "The last few races have been pretty good to Seb, but he hasn't had the rub of the green. So he will draw from that. He knows his day will come."