Compared with fellow grandees Red Bull and Ferrari, McLaren's pre-season is not running as smoothly.
After finding out that Mark Webber had done nearly 140 laps on Sunday in the new title-defending RB7, Lewis Hamilton described the feat as "crazy".
"I can only laugh," he is quoted by Auto Motor und Sport. "That's unbelievable. They're doing a really good job."
McLaren's radical MP4-26 joined the winter circus one test late and its ultimate performance is not yet clear.
"We urgently need to do a race simulation," the 2008 world champion is quoted as saying by O Estado de S.Paulo.
When asked how he feels about his new car, Hamilton answered: "It's ok, we are making progress. There's still a lot to come."
Jenson Button told The Sun: "I think it's unfair to judge us at this point because the amount of laps we have done is not massive.
"We really need some good days of running to really unlock this car."
France's autohebdo.fr quotes the 2009 world champion adding: "It seems like our base is good, but nobody will have a clear idea of where he stands until the first qualifying."