Jo-Wilfried Tsonga has accused an umpire of favouring Rafael Nadal during the pair's Sony Ericsson quarter-final in Miami.
The Frenchman was defeated by Nadal in three sets but he believes that he was treated unfairly by Damian Steiner and his fellow officials throughout the match.
Tsonga said: "He never takes initiative when it's against Rafa, you know. And, you know, now it's all the time like this. All the time.
"So I have to be really focused, you know, on the ball, because if the ball is out, it would never if it's really close, he would never say out against Rafa. Always to say against me."
However, Nadal responded by claiming that he does not receive preferential treatment from any umpires.
The Spaniard said: "Because that is true that the referees with the Hawk Eye are doing less overrules than before. I said hundreds of times, too, no? But is not because he's playing against me. No, no. Happen to me a lot of times."
Nadal will face Andy Murray for a place in the final in Miami.
