Mackenzie McDonald exhibited a rare tennis sight on Sunday after he served underhand during the quarter-final match against Canada’s Peter Polansky on Friday.

Serving at 3-5 down in the first-set tiebreaker, the 280^th-ranked American surprised one and all – his opponent included – by opting to ditch the customary overhand serve.

After his first serve crashed on to the net, McDonald didn’t mind going for it again on second serve. But, the more surprising thing was Polansky failing to return it.

McDonald would go on to win the first set (10/8) but it was Polansky who had the last laugh, prevailing 6-7 6-4 5-1 (retired) to make the last-four stage.

Polansky went on to pull off a 6-2 6-4 conquest of another American in Jared Donaldson before being downed in the summit clash, 7-5 2-6 6-1 by his third successive American adversary in Michael Mmoh on Sunday.

WATCH

#McDonald pic.twitter.com/K25Q3ZgX9Y

— doublefault28 (@doublefault28) November 11, 2016