Chinese GP: Button says only Ricciardo can challenge Mercedes

Although Ricciardo was only fifth in practice on Friday, Button was impressed by the Australian's long-run speed on a day when many - including McLaren - were badly hampered by tyre graining.

He expects Ricciardo to outshine four-time world champion team-mate Sebastian Vettel again and lead Red Bull's charge.

"Ricciardo in the Red Bull looks very strong," said Button.

"He's a lot quicker than his team-mate and able to do seven more laps [on a set of tyres] on long runs.

"He looks very good and his car's obviously working reasonably well on the tyres."

Ferrari was Mercedes' main rival on the timesheets, with Fernando Alonso quickest in practice one and then second to Lewis Hamilton in the afternoon.

But Button thinks Ferrari's performance was deceptive.

"I don't think the Ferrari is the car that will be fighting Mercedes. Maybe in qualifying, but for the race," he said.

"I tend not to look at just one-lap pace, because that's not what wins you races. It's long runs that win you races.

"[Alonso] is not fast compared to Ricciardo. The Red Bull is very consistent - 18 laps in the 1m44s.

"I think he's the guy that's really going to challenge the Mercedes, if anyone's going to challenge them."

Button expects the tyre issue to shake the Formula 1 field up at Shanghai, and admitted that McLaren is not currently in a position to benefit.

"It's going to be a bit of a mix-up, I think," he said.

"The difference is that some people are getting the tyres working and some aren't.

"A few cars out there are able to not grain the tyres and you can see their laptimes are much, much better than ours."