Watch: 'Go to practice, man!' - Marat Safin hilariously trolls Taylor Fritz during training session at Madrid Open

Known for his fiery personality during his playing days, retired Russian tennis star Marat Safin proved he hadn't lost a step after teasing Taylor Fritz during a practice session.

The former World No.1 is currently working with compatriot Andrey Rublev in a coaching capacity, as the two began their collaboration this month. However, their joint efforts have not yielded very positive results, with Rublev not going past the round of 16 since Safin joined his team.

Safin jokingly calls out Fritz's bad serves

In a viral clip posted to social media, Fritz was seen on the practice courts at the ongoing Madrid Open. The World No.4 was working on his serves when Safin grabbed a racket and stood in the opposite half of the court, ready to receive Fritz's serve.

However, the American missed his first serve, sending it crashing into the net.

"Oh my God!" yelled Safin in mock exasperation.

Fritz would proceed to hit a second serve, this time sending it long and past the service line.

"Go to practice, man!" said Safin as he appeared to storm off in frustration, much to the delight of those present.

Although Rublev lost his third round match in Madrid to Alexander Bublik, Fritz was able to defeat Frenchman Benjamin Bonzi and now faces Norwegian Casper Ruud in the round of 16. There is no word on if Safin will be present to judge the American's serve during the match.