World No. 1 Novak Djokovic got off to a dreadful start against Musetti and found himself trailing by two sets. But the Serb raised his level while Musetti's simultaneously dipped, allowing Djokovic to take the next two sets in 46 minutes.
Djokovic appeared to be coasting to victory in the fifth set, but Musetti retired due to an injury just before the Serb could cross the finish line.
Speaking on Eurosport, six-time Grand Slam champion Becker said the Italian should not have retired when he did as he did not suffer a "bad injury".
"I haven't seen a very bad injury," Becker said. "That's why I don't think it's good to stop. You should have respect for the other player and say 'He beat me today'. Then it's 6-0. It's a test of maturity. But athletically, he can absolutely keep up."
Novak Djokovic will face another Italian in the form of Matteo Berrettini in the quarterfinals on Wednesday. Berrettini will enter the match with an extra day of rest after Roger Federer gave him a walkover in the fourth round.
Becker believes this would give Berrettini an advantage against the World No. 1.
"For me [in the quarterfinals], it’s advantage Berrettini," said the German. "He has an off day now and had long matches before. Now he has watched the match very closely and he saw Djokovic is beatable."
Novak Djokovic had problems with Lorenzo Musetti's style of play: Boris Becker
Lorenzo Musetti did not hit the ball particularly hard, but his slices and underpowered returns caused plenty of problems for Novak Djokovic. Struggling to generate his own pace, the Serb failed to assert himself in rallies in the first two sets.
Boris Becker said Djokovic struggled to deal with Musetti's gamestyle.
"Novak had problems with Musetti's style of play," opined Boris Becker. "He does everything quite well. He doesn't have the big weapon, but the serve is okay, the movement, the technique and also the confidence because he had already won many matches this year."
Becker believes Lorenzo Musetti and Jannik Sinner are the best teenagers on tour. But the German stressed they have their task cut out against top players as they are not yet physically and mentally ready.
"You always have to keep at it and believe in yourself from start to finish, especially against the big guy," added the German. "Lorenzo Mussetti is the best teenager, together with [Jannik] Sinner. When you face the biggest on the scene, you have to be ready physically and mentally. The young guns don't understand that. It's not just playing tennis, it's about character and personality."
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