France's Jo-Wilfried Tsonga accused a chair umpire of favouritism towards Rafael Nadal after the Spanish World No 2 won a marathon three-setter to reach the Miami Masters semi-finals.
Tsonga claimed that match official Damian Steiner was reluctant to over-rule calls affecting Nadal.
Tsonga said: "I was complaining because all the match I have to challenge, and I was right, many, many times.
"He never takes the initiative when it's against Rafa. So I have to be really focused on the ball. If it's really close, he would never say out against Rafa. If Rafa don't like him anymore, he'd not be in the chair many times in the final and semi-final."