set point 
noun
(In tennis and other sports) a point which if won by one of the players or sides will also win them a set: his brilliant ace denied Sampras the set point...
- In the tiebreaker, he finally converted on his third set point when the Swiss swatted a backhand long.
- The Russian finally clinched the set on her fourth set point when Williams dumped a tame forehand return into the net.
- Moya took a 6-3 lead in the tiebreaker, but couldn't capitalise on three set points as Agassi evened the score.