PHILLIP ISLAND (AFP) - Australia's Casey Stoner sealed the MotoGP world title Sunday with victory at the Australian Grand Prix as his closest rival Jorge Lorenzo pulled out with a sickening finger injury. The Honda rider's fifth consecutive win at Phillip Island was enough to clinch his second career championship with two races to spare after defending title-holder Lorenzo, his closest challenger, crashed during the warm-up. While the Spaniard was flown to Melbourne for surgery to reattach the ring finger on his left hand, Stoner powered away from pole position on the grid in a wire-to-wire win as he celebrated his 26th birthday in style. "It's a shame what happened to Jorge this morning -- it's not the way you want to win a championship," Stoner said. "But we had momentum and we felt we were going to win anyway." Stoner dominated his rivals over the three days at Phillip Island on his factory Honda and never looked like losing a race in which he is now unbeaten since 2007 -- the year he first won the championship on a Ducati. And Lorenzo's withdrawal meant the Queenslander only had to finish in the top six to wrap up the title, with races yet to come in Malaysia and Valencia. Stoner opened up a big lead on the first lap and held on despite having to battle treacherous conditions when rain began to fall three laps from the finish. The Australian slowed right down to ensure he didn't come off his bike and eased to a two-second win over Italian pair Marco Simoncelli and Andrea Dovizioso, both on Hondas. The colourful Simoncelli then spent the remainder of the race fighting over second with Dovizioso, the pair changing positions a number of times with Simoncelli only clinching it on the last lap. Spaniard Dani Pedrosa was 10 seconds adrift of Dovizioso in fourth.