WATCH: Medvedev hits hot shot, umpire's chair in same match

Though Daniil Medvedev has been a big name on tour for a while now, the tennis world is in a lot of ways still figuring him out. This is probably due to his propensity to one minute challenge the physical boundaries of what's possible in the sport, and another minute act, as The New Yorkerput it, "like a clown, or worse."

In Thursday's ATP Cup quarterfinal, in Sydney, Medvedev played what was maybe the best point of the day, and he was also the culprit of the day's most disturbing moment.

Let's start with the positive part:

Seven minutes in, playing Argentina's Diego Schwartzman with the opportunity to clinch the tie for Russia, Medvedev sliced a serve wide, and Schwartzman answered with an impeccable return that went even shorter and wider. This sent Medvedev sprinting far off the in-bounds part of the court, where he whacked a forehand around the net post—the net was hardly in sight. Schwartzman, who always shows deft defending, chipped a backhand back over, but it wasn't enough to beat Medvedev, who'd make it all the way to the other coast of the court in time for the backhand putaway.

Medvedev went on to win the match, 6-4, 4-6, 6-3, and securing the semifinals spot. That middle set, though, is where things got dicey.

During a protracted argument with chair umpire Mohamed Lahyani, Medvedev twice smacked Lahyani's chair with his racquet, for which he received a point penalty.

It was the latest of a number of unsavory incidents at the ATP Cup, following an angry display by Alexander Zverev, and Stefanos Tsitsipas accidentally hitting his father with a stick smash. Among the tournaments' best-behaved stars, it seems, is Nick Kyrgios, who faces a suspension should he get a code violation for unsportsmanlike conduct or related offenses.

Despite the detour, Russia won all three matches versus Argentina. The team faces Serbia in Saturday's semifinals. Medvedev, for his part, might do something sublime—or he might do something cringe-causing. He'll likely even do both.