Big men fall hard for grass but Djokovic, Murray still hold the aces Theatre: Juan Martin Del Potro collapses after defeating David Ferrer in their quarter-final at Wimbledon. A clue to the likely outcomes of Friday's Wimbledon men's semi-finals may be found in the eloquent body language at the end of the quarter-finals. Juan Martin Del Potro and Jerzy Janowicz, both immensely tall men, collapsed like crumbling sandcastles and buried their heads in Wimbledon's sweet grass. Del Potro crumpled so theatrically it was a wonder he did not do more damage to the wrenched knee that nearly ended his match against David Ferrer early. Janowicz, when at last he rose, hugged the man he beat, friend and compatriot Lukasz Kubot, so hard that Kubot must have struggled for breath. Del Potro and Janowicz both cried, and struggled for words in any language. Both had won in straight sets. Novak Djokovic also won in straight sets, against Tomas Berdych, and celebrated in the ATP-approved manner, with a discreet fist pump, in the upright position. Andy Murray's victory over Fernando Verdasco was anything but straightforward. When it was done, his relief - personifying his nation's - was apparent, but also his self-possession: no sprawling on the grass for him, just a few autographs to sign, before he got to his warm-down bike. When defeat threatened, Murray said, only the fact of defeat had concerned him, not that it would mean the end of his Wimbledon. He stayed in the moment. For Djokovic and Murray, ranked No.1 and No.2 in the world, quarter- and semi-finals, no matter how dramatic, could only ever be waystations on the road to the final. Murray wants Wimbledon, desperately, and Djokovic wants it again. Their hegemony is more assured than ever. For Djokovic, now it is about empire building, for Murray and the British crowd, it is about reclaiming empire. For Del Potro and and Janowicz, a semi-final is a destination. Janowicz is just 22 and has never been to one. Del Potro has, but not since he won the US Open in 2009. Injuries have wracked him since, and may yet thwart him again here. "Right now, I'm the most happy person in the world," Janowicz said after beating Kubot. I made semi-finals of grand slam. It's not easy to control all the feelings inside my body. Of course, it is not as simple as to say that Djokovic and Murray are more accomplished players with more to play for here, nor would either be blithely presumptuous. Del Potro beat Djokovic in the Olympic bronze medal match on this court last year, and Janowicz beat Murray at their most recent meeting, last year in Paris. "The pressure will be different this time," Del Petro said. I know it. I will have to be 100 per cent, or 110 per cent against him. There is about these semi-finals the merest sense of guard-changing. From the final four at the Olympics on these courts last year, Janowicz replaces Roger Federer. Janowicz is the youngest and least performed of the quartet. When his eyes dried and his heart and mind at last stopped racing on Wednesday, he said: "I'm really happy to reach this far in Wimbledon - but I hope deep down I will still get two more matches."