Australia's MotoGP world champion Casey Stoner has launched a stinging attack on Italian icon Valentino Rossi following Rossi's move back to Yamaha.
Rossi will saddle up again with Yamaha after a failed campaign with Ducati, on which Stoner won his first world title before switching to Honda.
Stoner has accused Rossi of failing to ride the bike to its limits and castigated the multiple world champion and his Australian crew chief Jeremy Burgess for boasting they could produce a Ducati on which "any rider could win."
"They ate their words from day one," Stoner said on Wednesday.
"Jerry saying that it would take him 80 seconds to fix that bike and that it was a simple issue and now they have had almost two years and have not made any inroads.
"Valentino obviously doesn't want to push limits and ride a bike that is not perfect, he has admitted that.
"Obviously he doesn't want to put the effort in with Ducati."
In his most recent race Rossi was eighth and 10 seconds behind teammate Nicky Hayden when he crashed out of the US GP.
In his first stint with Yamaha - from 2004 to 2010 - Rossi won 46 races and four world titles.
In a stunning back-flip Rossi is walking away from a reported $A35 million deal at Ducati to take a pay cut to return to Yamaha.
The seven-time world champion failed to win a race on the machine in his 22 months with the team.
Although now with Honda, Stoner remains a hero in the eyes of Ducati fans, having won 23 races and the 2007 world title with the red team.
There have been months of tensions with Rossi citing a lack of development work by Ducati engineers while he has floundered to master the unique style of the bike.
"I just feel completely sorry for Ducati that Valentino has gone there and done nothing but complain about the bike for almost two years," Stoner said.
"The amount of times that guy has had to eat his words is not funny, but people still forgive him for it."
Rossi will now have to take the backseat behind his rival, Spaniard Jorge Lorenzo.
"Our main investment is in Jorge and he is the No 1 candidate to be champion both this year and next year. He is our No.1 rider," said Yamaha MotoGP boss Lin Jarvis."