Novak Djokovic was furious after being asked to undergo a dope test shortly before Serbia's Davis Cup win over Great Britain, although the International Tennis Integrity Agency (ITIA) said on Saturday it was standard practice and he had not been singled out.
The record 24-time men's Grand Slam winner revealed his anger at being asked before the 2-0 win on Thursday which sent Serbia into the Davis Cup semifinals, rather than after.
Djokovic said officials asked for samples 90 minutes before his straight sets 6-4, 6-4 win over Cameron Norrie.
"I didn't believe that they could make such a decision, in 20 and more years of my career, it never happened to me that an hour-and-a-half before the match, I needed to go for doping control," the 36-year-old told Serbian reporters.
"I have my own routine -- I don't need that distraction, to have my urine and blood taken, to think about whether I can give urine at that moment."
Djokovic said he had no problem with being tested "a hundred times" but not before the match.
STANDARD APPROACH
However, the ITIA said the whole team was subject to testing and it was a standard approach for team tournaments.
"Due to the format of team competitions, including the Davis Cup, teams may be notified that they have been selected for testing before matches begin and then provide samples when they are ready," an ITIA spokesman told AFP.
"Between notification and providing the sample, they are chaperoned by a member of the anti-doping team."
World number one Djokovic was already in bad humour after a run-in with some British fans during his victory over Norrie.
The ATP Finals champion told them to "shut up" and show "respect" to players after they tried to drown him out with drums during his post-match victory speech.
Serbia face Italy in the Davis Cup semifinals on Saturday with Djokovic set to face world number four Jannik Sinner in the second singles rubber.