SHEFFIELD (England) (AFP) Australian Neil Robertson fired in a break of 107 to wrap up a 13-5 win over six-times former champion Steve Davis on Wednesday to reach the world championship semi-finals. Robertson, who had led 12-4 overnight, was briefly delayed after Davis took the opening frame of the afternoon with a break of 59, but he took his first real chance to clinch his place in the last four, where he will meet Ali Carter who beat Shaun Murphy 13-12. Davis had caused the shock of this tournament by knocking out last years winner John Higgins in the second round, 21 years after his last Crucible triumph. But Robertson was in equally buoyant mood after fighting back from 11-5 behind to oust Martin Gould 13-12 and the Australian always looked in control of the contest. I think the match against John Higgins maybe took it out of Steve a little bit, Robertson said. I was a little bit disappointed I didnt wrap it up last night. But all credit to Steve for taking it to the extra session. I was very relieved to get through because I havent played very well at all. Im over the moon to get to the semis considering the way Ive played so Ill have to improve a lot to get to the final. Davis admitted there was no way back after he ended the opening session of the match trailing 7-1. Sometimes matches are won or lost early on and I think I lost it in the first session, he said. I had a rotten, rotten session. It started with a kick. Mark Selby sent red-hot favourite Ronnie OSullivan crashing out. Selby has become an irritant to three-time world champion OSullivan after making a habit of fighting back to beat him in major finals. The Leicester player won 9-8 from 8-5 down against OSullivan in the 2008 Welsh Open and then 10-9 from 9-6 behind at Januarys Wembley Masters. This was another example of his refusal to accept looming defeat, as Selby won the final four frames to earn an 13-11 victory. After the Masters defeat at the start of the year OSullivan suggested neither he nor Selby would be capable of winning the world title due to their shared bold, attacking approach. Selby now faces former winner Graeme Dott, who came back from 12-10 down to edge his quarter-final with Mark Allen in the 25th frame. Dott, 32, now has the chance of a third Crucible final appearance having been runner-up to OSullivan in 2004 before beating Peter Ebdon to lift snookers biggest prize two years later. The Scot has since struggled with bouts of debilitating depression but he looks to be firmly on track for a return to the top following a victory that will lift him back into the worlds top 16. Northern Irelands Allen reached last years semi-finals in Sheffield and looked set to return when he moved to within one frame of victory. Dott responded with a break of 115, drew level and clinched the decider with a break of 41. It was a great game, the Scot said. I said to Mark when the referee was setting up the balls at 12-each that I had thought it was going to go that way. The two of us both played really well and just hit each other constantly for two days. My temperament is pretty good and I never let it bother me, and I knew if I got a chance that I was playing well enough to take it. That was the match that gets me back into the top 16. If Id lost that match 13-12 it would have been hard not being in the top 16. But Im over the moon. Ive got a lot of points, a lot of money and Im in the semis, so Ive got a chance to win it. A disappointed Allen said: I didnt turn up for the match at all, in any of the three sessions. I didnt play anywhere near my best. From 12-10 Graeme played three perfect frames really and deserved to win. I didnt score anywhere near the way I had in the first two games. Allen remains in contention for the tournaments 10,000-pound highest-break prize, thanks to his 146 in his second-round win over Mark Davis.