Casey Stoner's injury has left the MotoGP world championship path wide open for Jorge Lorenzo, but the Spanish rider says he wants a fight to the flag, not a stroll.

Stoner, the out-going champion, is sidelined with an ankle injury and will miss this Sunday's San Marino GP having also been forced out of last month's Czech GP because of surgery.

His absence has all but reduced the season to a duel for the crown between Lorenzo and fellow Spaniard Dani Pedrosa.

Until Stoner was injured in Indianapolis, he and Lorenzo had dominated race wins this season with a combined nine victories - Lorenzo with five and Stoner with four from 12 races.

Yamaha No.1 Lorenzo, the 2010 champion, concedes that he will miss Stoner's intense commitment to winning.

"I think without this crash Casey would have been fighting for the championship," Lorenzo said.

"I would prefer to beat him on the track, not while he is away, and this year as always he was pushing very hard to win the championship.

"But as we all know in this sport if you are close to the limit there are some more chances to crash. I know this feeling.

"But this is a sh*t situation for Casey as he will retire at the end of this season and he now has no chance to race for the title."

Pedrosa has won the past two races in the Czech Republic and Indianapolis and he now trails Lorenzo by 13 points.

There are six races remaining including next month's Australian GP at Phillip Island for which Stoner hopes to be fit.

Stoner has slipped to 59 points behind Lorenzo with no hope of making up lost ground in his final season of MotoGP.

Pedrosa, who is in his seventh season at Honda but bidding for his first title, goes to Misano this weekend with an improved suspension and electronics package on his Honda.

But Lorenzo is the defending winner from last year with the convoluted and bumpy Misano circuit expected to suit his Yamaha M1.