LONDON, July 3 (Reuters) - When his left leg jarred horribly and towering Juan Martin del Potro fell to earth after five points of his Wimbledon quarter-final against David Ferrer on Wednesday there seemed no way back.
Remarkably, a little over two hours later, with the help of some "magic" pills provided by the tournament doctor, the six foot six Argentine wrapped up a superb 6-2 6-4 7-6(5) victory to reach the semi-finals at the grasscourt slam for the first time.
Quite what sort of shape his left knee will be in when he walks on court against world number one Novak Djokovic is any one's guess - that is if he makes it that far.
"I'm not going to put my body at risks, you know," the eighth seed told reporters.
"The doctors tell me with this tape and taking some anti-inflammatories you can play.
"If they say something different, I will think."
It would be terribly cruel on the 24-year-old if injury prevented him taking on top seed Djokovic because the way he responded to adversity against the tenacious Ferrer was nothing short of breath-taking.
Using his condor-like wingspan to make up for any lack of movement, Del Potro unleashed his right arm to deliver a barrage of mighty serves and thumping forehands.
His forehand was unplayable at times and it was fitting that he finally broke the dogged resistance of fourth seed Ferrer with his 22nd scorching winner from that flank after a dazzling rally that had both players at full stretch.
"I made my best forehand ever I think in this tournament to beat David," said Del Potro whose form was reminiscent of when he won the 2009 U.S. Open.
"It's my first semi-finals here, another semi-finals in grand slam after couple of years. I think I'm in the fight again with the top guys."
It looked unlikely when del Potro raced across the baseline to retrieve a Ferrer shot at 15-40 in the opening game and fell spectacularly, re-injuring the knee he hurt in his third-round match against Grega Zemlja.
"It's not easy when you're in the quarter-finals, centre Court, and the match has just started. I think I was close to retiring," he said.
"Many things come to my mind, many bad things. But I tried to be positive and played unbelievable tennis. I was lucky because I did everything good."
Del Potro spent a while laid out on the turf behind the baseline before walking gingerly to his chair where he was given an anti-inflammatory tablet.
"The doctor said they couldn't do any more with my knee. I had the tape, a very tight tape, and that helped me to move a little bit, but nothing more.
"I took some anti-inflammatories to continue playing, but was really painful in the beginning of the match."
All eyes were on Del Potro's movement in the opening few games and he looked far from mobile as Ferrer tried to stretch him wide, particularly on the backhand side.
Even when fully fit the six foot six inch Del Potro appears to lumber around the court, although his speed is deceptive.
Forced to take the initiative to avoid getting the runaround by the relentless Ferrer, who will become world No.3 on Monday, Del Potro cranked up his forehand at every opportunity.
The bandaged Del Potro broke twice to win the first set and clinched the second after Ferrer cracked under pressure at 4-4, slicing a weary-looking backhand into the net after another onslaught from the Argentine.
Ferrer seemed to lack his usual zip, possibly because of a toe injury that has been nagging him since reaching the French Open final, but he hung on grimly to force a third set tiebreak.
Del Potro sensed danger when he was 15-30 down on his serve at 4-5 but delivered a towering ace that Ferrer referred to a Hawkeye challenge more out of desperation than genuine hope.
Ferrer fell behind in the tiebreak but again dug deep to put pressure on Del Potro.
There was no escape, however, and after a long baseline rally which had the players scrurrying from side to side, Del Potro launched a forehand missile to clinch victory and this time collapsed to the turf in joy rather than pain.
"I will need to be 100 percent or 110 percent against (Djokovic)," Del Potro said of the challenge of facing the man he beat in an Olympic bronze medal match here last year.
"But I will try to be ready and do my best." (Editing by Ed Osmond)