Emma Raducanu says she was fighting against jet-lag during her three-set 6-2 3-6 6-4 opening round victory against Elise Mertens at the Mubadala City DC Open in Washington.
The 21-year-old, in her first appearance since a Wimbledon last-16 defeat earlier this month, won five straight games to take the first set but Mertens, the eighth-seeded Belgian, responded well to take the second set.
Having arrived on the east coast of the United States from the UK on Thursday, Raducanu was battling a five-hour time difference as the final set went past 11pm.
But the former US Open champion showed her mental resolve to win the last set, saving five break points at one point to overcome Mertens for the second this month following a win at Wimbledon.