Casey Stoner believes team-mate Dani Pedrosa is finding motivation for a MotoGP return difficult, after suffering so many injuries in recent seasons.
Pedrosa has been sidelined since breaking his collarbone at Le Mans in May, after a controversial clash with Marco Simoncelli, and has now undergone two surgical procedures.
"This is a bad situation, Dani having to go back for more surgery," said Stoner. "If it was a clear situation maybe he would be back already, but another surgery makes things a lot more complicated for him.
"And by the sounds of it, it's difficult for him to find motivation to come back and ride again, when he's been so unlucky with injuries and to have this situation happen to him again."
However, Stoner doesn't believe that winning this year's championship will now be an easier task.
"I don't think it's going to make the championship easier without Dani," he said. "I've still got a lot of competitors, although Dani would have added to it for sure."
Stoner winner of four of the first six races of this year, holds an 18 point lead over Yamaha's reigning world champion Jorge Lorenzo heading into this weekend's Assen round.
Lorenzo and Pedrosa are the only other riders to win a race this year.
Pedrosa, last year's world championship runner-up, has been replaced by Hiroshi Aoyama this weekend.