Mahut made the biggest move of the day thus far in the 137th game of the set, hitting a huge inside-out forehand to go up 0-30.
But predictably, Isner cleared the game to 30 win four unreturnable serves, quickly reversing the swing of momentum in a way more meaningful than anyone could have realized at the time.
Mahut’s 69th service game of the set started with an Isner forehand up the line that Isner thought was a winner, but was called out by the line judge, a call affirmed by chair umpire Mo Layani.
At 15-0, Mahut hit a forehand long for an error at a neutral point in the rally to even the game.
At 15-15, Isner slipped to the ground behind the baseline, but the drop shot that Mahut attempted to take advantage sunk to the bottom of the net.
At 15-30, under pressure, Mahut bravely ventured to the net, and finished the point with a touch volley for 30-30.
Mahut came to net again at 30-30, but was passed by a great Isner forehand up the line to give Isner his fifth match point.
And on that fifth match point, his first of the day, Isner finally ended it with another up the line passing shot winner, this one off the backhand side.
Isner collapsed to the ground in joy, a celebration more pronounced and more deserved than the usual fare saved for winning a slam.