[3] Krstin has a career high ATP singles ranking of No.

He also achieved a career high ATP doubles ranking of No.

He has won one Challenger and 14 Futures singles titles in his career.

Krstin made his ATP main draw debut at 2014 PBZ Zagreb Indoors after defeating Marcos Baghdatis, Gianluigi Quinzi and Martin Fischer in the qualifying rounds before losing to compatriot Dušan Lajović in the first round of the main draw.

[5] He received a wildcard for 2021 Serbia Open and won his first round match against Korean Kwon Soon-woo, who was ranked No.