MASON, Ohio — Derek Dietrich sat nearly silent in the second row of Court 10 at Lindner Family Tennis Center, his concentration on his girlfriend, Monica Puig, who was well into the second hour of her qualifying match against Anastasia Potapova on Saturday.



Puig, after losing a point in the third set, fell to her knees, exhausted. Potapova had already taken an injury timeout to deal with her shoulder, but Puig couldn’t put her away.



Dietrich watched her intently but didn’t yell out his support. He hadn’t done so for any of the match, his most outward emotion being some claps at one point and a few mouthed encouraging words. But here in the third set, it was on Puig.



“I like to say if you’re not in the arena or on the field, you really don’t quite know or understand,” Dietrich said a couple of days before that match.



At that moment, he understood. He saw Puig push through her fatigue and pain to come...