Former McLaren tester Gary Paffett is unsure of the British team's potential as its new works Honda era begins.
After years of serving as tester, McLaren's change of power means Briton Paffett, who will remain Mercedes powered in DTM, has left the Woking team.
McLaren is now working with Honda, its ultra-successful partner of the 80s.
To succeed, Honda will need to reach Mercedes' level, which will be very difficult.
"The last (McLaren-Honda) time was very successful," Paffett told f1web.it, "but it is now more difficult to make predictions.
"McLaren also needs to make progress with the chassis, as in recent years, the car did not meet the expectations of the team," he added.