Alessandro Petrone vividly remembers a rainy day in Sanremo three years ago during the Covid-19 pandemic. Running along the water was a young Matteo Arnaldi.

“He was running on a road along the sea under the rain. I thought, ‘Wow, this guy is amazing. He’s running under the rain in the COVID times,’” Petrone told ATPTour.com. “I think he really has something special, so that’s what gave me the trust in him.”

Petrone has coached Arnaldi since 2021. Now they are enjoying the best week of their partnership, as the 22-year-old is into the fourth round of a major for the first time at the US Open. The Italian will next play top seed and defending champion Carlos Alcaraz.

“I think Carlos has reached a very high standard of play. So for sure, he will play amazing, he will be very focussed. Of course it’s the second week of the US Open, so it’s not the first round. Maybe sometimes some of the top players at the beginning of the tournament can be not distracted, but more relaxed in some way,” Petrone said. “I think the most important [is how] Matteo will play.”

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It has been a breakthrough season for the Sanremo-native, who last year competed in the Next Gen ATP Finals. At the time, he was the No. 134 player in the Pepperstone ATP Rankings. Now Arnaldi is No. 47 in the Pepperstone ATP Live Rankings and climbing.

According to Petrone, a pivotal moment for his charge came at the Mutua Madrid Open. Still yet to crack the world’s Top 100, Arnaldi qualified, defeated Benoit Paire in a final-set tie-break in the first round of the main draw and then stunned Casper Ruud in straight sets in the second round.

“Mentally I think after beating Ruud in Madrid, now he really has the confidence that he can play at this level and beat the top players,” Petrone said. “I think the way he played with Ruud was unbelievable with more than 45 winners. That was an amazing match.”

Arnaldi has continued his progression since then, defeating former Top 10 star Diego Schwartzman in Rome and advancing to his first ATP Tour semi-final in Umag, where he lost to eventual champion Alexei Popyrin in three sets.

“Of course it’s better. We are working and we are trying to improve of course the serve and his forehand. Those are the main aspects where we are working on,” Petrone said. “Also on the return because at this level everyone is serving amazing. So I think these are the main aspects we are working on and he is improving a lot.”

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That was apparent in Arnaldi’s third-round victory over British No. 1 Cameron Norrie, the 16th seed and a former major semi-finalist. The Italian converted five of his six break points to triumph in straight sets.

“I think he doesn’t care too much who he is playing,” Petrone said. “He’s very confident in himself and he really likes difficult challenges. He just played one of the best matches in his young career.”

Off the court, Arnaldi almost always has a smile on his face. After he defeated Norrie, the 22-year-old was placed in the US Open’s main interview room and clearly took in the experience.

“He’s always smiling because I think he really enjoys what he’s doing… He really likes the professional player’s tennis life, and that’s why he really enjoys it,” Petrone said. “For him, he doesn’t feel restricted [when he has to] go to the gym, to practice and to do everything. So I think this is the key. He has a lot of passion, a lot of determination on the court, in the physical trainings, in the diet and sleeping.

“His idol is Djokovic and so I think he wants to be as similar as possible to him in these things.”

Arnaldi will try to channel Djokovic on Monday when he plays Alcaraz for the first time.

“I think he just needs to enjoy every moment there. This is something that will help him in the next months and then maybe of course the next years when he will face other top players. So I think he just has to enjoy it,” Petrone said. “Of course, focussing on what he has to do in the tactics and the strategy, we will prepare that tonight. I think the most important thing is that he enjoys the match, he enjoys playing with Carlos, he enjoys playing with all these people in the best stadium in the world. I think from how I know him, I’m sure he will do it.”