In 2017, Popyrin began training at Mouratoglou Academy. After winning the Junior Roland Garros title, his career took off. In 2019, Alexei won at least a round in all four Grand Slams and broke into the ATP Top 100 for the first time. He also successfully qualified for 10 ATP main draws, which is more than any other player on the tour (tying Mischa Zverev in 2016), showing tenacity, consistency, and enormous potential. In 2020, Popyrin competed in UTS alongside some of the world’s top tennis players, earning wins against experienced players like Benoit Paire and Feliciano Lopez. He received the nickname “The Sniper” because of his dangerous serve and ability to perform under pressure.