Key Biscayne: Britain's Andy Murray fought back for a 4-6, 6-3, 6-4 win over Serbian Janko Tipsarevic on Wednesday to reach the Sony Ericsson Open semi-finals.   

Murray, the world number four, trailed by a set and a break before receiving medical attention for what appeared to be a stomach problem.   

The Scot then promptly turned the match around as he broke the next service game from ninth seed Tipsarevic and went on to clinch the second set.    

Murray, whose backhand was below par and who made 34 unforced errors, then broke in the third game of the final set and held firm with his serve to ensure a last-four match against Rafa Nadal or Jo-Wilfried Tsonga, who play later on Wednesday.   

Murray said after the game that his health problem was almost certainly related to over-hydrating before the game.   

"I have this thing that tests how hydrated you are, which I used that for the match, and (afterwards) I was very hydrated, even though I'd drunk nothing the last couple of sets.     

"So I don't know if I drunk too much beforehand and kind of overhydrated and my stomach was filled with liquid. Each time I took a sip I wanted to burp, basically.    
"I drank very, very little the last two sets. I mean, must have been something to do with that. It was so hot and humid, and to come off the court hydrated after not really drinking would probably suggest that I had drunk way too much."