New coach Ivan Lendl brings out the bulldog spirit in buoyant Andy Murray ahead of clash with Rafael Nadal "I have to recover well and improve my knee if I really want to have any chance to win," said Nadal, whose left knee has been bothering him since Indian Wells a fortnight ago. If not, it's going to be almost impossible. Nadal may have been short of his absolute best in this tournament, but even at 80 per cent he still makes a bulldog of an opponent. The best way to beat him is to blitz him at every opportunity, to force him further and further back behind the baseline. So this match will be a revealing test of Murray's new, increasingly assertive style of play. In his own match on Wednesday, Murray overcame stomach trouble to score a scrappy but satisfying win over Janko Tipsarevic. It showed that he can overcome the sort of niggling physical issues that have sometimes derailed him in the past. "In golf there is a saying that when people whine about their scores, or make a par by chipping in, "there are no pictures on the scorecard,"" said Lendl, who was renowned for his physical toughness. It's a win. Whether you have a tummy, or a broken leg or whatever, one guy goes through and it had better be you. In the women's semi-finals, Maria Sharapova benefited from an umpire's disputed overrule on match point to defeat Caroline Wozniacki 4-6, 6-2, 6-4. At 5-4 and 40-30 in the final set Sharapova hit a second serve that the linesman called long. It would have been a double fault but the umpire reversed the ruling and ordered the point to be replayed. TV replays indicated that the ball was out but the Dane had no challenges left. The Russian was awarded two serves and took advantage to set up an overhead winner for the victory. Wozniacki declined to shake the umpire's hand and had words with him as she walked to the exit.