The ATP is to review the scheduling of matches after Andy Murray's meeting with Philipp Kohlschreiber in the Madrid Open began at 01:12 local time.
Several lengthy matches on Wednesday night forced the late start of Murray's second-round victory.
Murray's 6-4 3-6 6-0 win finished at 03:00, and he is due to face Spain's Marcel Granollers on Thursday evening.
"The scheduling issues in Madrid were unfortunate," said ATP Tour chief executive Chris Kermode.
Murray's match was delayed after Roger Federer's three-set defeat by Nick Kyrgios took two hours and 37 minutes, while Granollers needed three hours and 20 minutes to beat Gael Monfils.
Kermode admitted that players starting after 1am were at a "disadvantage", but that scheduling involved juggling the interests of players, promoters, ticket holders, TV broadcasters and media.
"While such instances are rare, we will look at reducing the risk of similar instances occurring in the future," Kermode added.
Murray and Kohlschreiber's meeting in Madrid was just two days after the Scot had beaten the German in the final of the Munich Open, which had been carried over from Sunday due to rain.