Svitolina is seen as quiet, serious and reserved — characteristics she said she gained while training in Kharkiv, Ukraine. Monfils, raised on the French Caribbean island of Guadeloupe, is jovial and exuberant, one of the more charismatic players on tour.

He has pushed back on a theory that his lighthearted demeanor and predilection for trick shots mean that he is not serious about tennis, yet he said in the ESPN interview that Svitolina has brought “more discipline” to his game.

“She is a hard worker, very professional,” he said. “Sometimes even too professional, I think. Because there has to be a balance. Definitely I bring a little bit more joy to her, but she will bring me more discipline as well.”

Because both fall more on the defensive end of the tennis spectrum — “we are hustlers,” Svitolina said — they often share insights and tactics.

“We are really different in our approach to some things, but we understand each other really well, and the difficult situations we’re always facing,” Svitolina said in an interview Tuesday. “There are lots of challenges throughout a tennis career; almost every week you are losing, so you have to be mentally strong and fresh each week, because everyone is hungry to beat you.”

Besides their shared careers and goals, Svitolina said she has found a lot in common with the Monfils she has come to know away from the spotlight.

“When I first got to know him, I was actually very surprised,” she said. “Because what people think of him and what they say, he’s a very different person from that when the door is closed. He’s open, but he thinks a lot, analyzes a lot. He’s very different with me when we’re alone.”