Suzuki legend Kevin Schwantz says Andrea Iannone just "needs to get on with the job" after a dismal first half of the 2017 MotoGP season.
Iannone joined Suzuki for this year after two seasons at the works Ducati team that included a race win, but he has taken only four points finishes - none higher than seventh - so far this year and is 16th in the standings.
Asked what he thinks about Iannone's performances so far this year, Schwantz said he needs to stop complaining about the shortcomings of his GSX-RR.
"I'd be happy to tell him what we all see, what everybody sees and everybody thinks," said the 1993 500cc champion, who spent his whole top-level career with Suzuki.
"He may not like what he hears.
"I spoke to him in Austin and he said he just can't believe it, because the bike doesn't stop, doesn't start and doesn't turn.
"Doesn't sound like it's much good, but he was OK in testing.
"In Qatar, he ran into the back of somebody [Marc Marquez] in the middle of the corner, the bike cornering was pretty good there.
"He just needs to be told get on with the job, sometimes it is hard work.
"It's easy for him to sit in his chair and see the Ducatis doing as good as they are and say 'woah, I should still be there'.
"Don't forget, they fired you, they sent you packing!
"You don't have that opportunity anymore, so make the most of what you've got."
When Schwantz's comments were put to him, Iannone pledged to respond to the criticisms with "my actions on track".
"I don't know what to say about Kevin," said Iannone. "I've always respected him as a person and as a rider.
"I'm sorry for what he said, I would rather he had said these things to my face as we work for the same company.
"I accept his criticisms and I intend to respond with my actions on track."
Suzuki signed Moto2 star Alex Rins to race alongside Iannone this year, but the rookie's season has been severely hindered by injuries that sidelined him for five races.
Schwantz is hopeful Rins will return from the month-long summer break before Brno in better shape so he can fulfil the potential he showed in the lower categories.
"Maybe this summer break will give Alex a chance to get fit, get his confidence back," Schwantz said.
"Maybe he'll come back after the break and be that young kid that Maverick [Vinales] was in the beginning and turned out to be.
"I'm not saying that I want Alex to be a Maverick, I want Alex to be Alex, I want to see what his true potential is and we haven't seen that."