Andy Murray converted on his seventh match point to beat Mackenzie McDonald in three sets and set up a second-round tie against fellow Brit Kyle Edmund at the Citi Open.
McDonald, 23, broke two of Murray’s opening three service games and wrapped up the first set 6-3 inside 40 minutes.
But Murray drew things level, taking a crucial game nine in the second for a 5-4 lead and serving out the set.
A 73-minute deciding set followed, in which Murray took an early break and found himself 5-4 up and serving for the match.
But McDonald saved five match points and converted his second break point to draw things level at 5-5.
Murray broke back immediately for a 6-5 lead following a controversial call when McDonald’s racket was adjudged to have crossed the plane of the net at 30-30. The former British No 1 then made no mistake in serving out the match.
“It was a tough, tough match,” Murray told the ATP Tour website.
“It could have gone either way. Obviously, if you lose a match like that, it’s a tough one.