Arnaldi, who has battled a lingering right foot injury as his ranking plummeted over the last six months, was 0-5 at tour-level for the season at the time. By the end of the week in Sardinia the former world No.29 had five much-needed wins, including one in the final over Hubert Hurkacz.

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Fast forward a month and the San Remo native is now into his first Grand Slam semifinal as the lowest-ranked man to get this far in Paris since 1997. He has done it in the most excruciating fashion. He has done it with heart, courage and grit.

“He surprised me,” Colangelo told rolandgarros.com on Thursday. “When we started it was a really tough moment. The injury was still something big for him, because it had been a long time since he could do what he wanted to do on court during the matches and in practice.”

Asked what has impressed him the most during his brief time spent coaching Arnaldi, Colangelo did not hesitate.

“What impressed me is how he enjoyed being in those difficult positions,” he said. “We were talking in Cagliari and he said, ‘I never played a match tiebreak in the fifth set in my career.

"I said, ‘Okay, maybe let's wait a little bit, because I had one last year with Sonego at Wimbledon – it’s tough.’ 

“When he had to play one against Raphael Collignon [in the third round], he turned to us and he was laughing because he was happy about it. I think this is special because he was serving for the match – he was up in the fifth – so it was a moment that you should be pissed, and he was happy, and he played an unbelievable tiebreak.”

Those marathon matches have totalled 19 hours and 42 minutes of court time for Arnaldi – a concerning number for a guy who still has to manage the foot issue that has plagued him of late. 

Since the statistic was first recorded, no player has spent as much time on court on the way to a Grand Slam semifinal. The previous record was held by Albert Costa who spent 18 hours and 31 minutes on the terre battue in 2003 before facing Juan Carlos Ferrero in a losing effort in that year’s semifinals. 

With two five-setters under his belt in rounds three and four, Arnaldi has smashed through the record and handled it surprisingly well. In a tournament full of shock upsets and surprising results, Arnaldi’s breakthrough might be the most stunning of all. 

After Wednesday night’s quarterfinal victory was cut short when Matteo Berrettini was forced to retire with a hip injury, Arnaldi admitted that he still isn’t quite sure how he’s going to hold up the rest of the way.

“Obviously it was a question mark today,” he said, explaining that he took Tuesday as a rest day to conserve what energy he has left. “I just came here, did some physio and some stuff in the gym. Today I was actually feeling pretty good.” 

Even if the fatigue is setting in, the adrenaline of making a career-changing run is keeping Arnaldi’s spirits high. 

“I can't complain,” he said. “I have been playing a lot but at the same time, I'm happy to be on court and to spend time on court, because I missed playing. I for sure have some energy left for the next matches.”

Asked to describe his emotions after moving through to the semifinal, he said, “I still can’t believe it. If I think about where I was a month ago, I was almost No. 150 in the world. Then I played the Challenger in Cagliari and from there I started to feel better and train again like I wanted. 

“Now I’m here. It’s crazy to think, but I always liked this tournament and I always play well here. Two years ago I made the fourth round, so I love to play in front of this crowd.”

Arnaldi’s next challenge, against No. 10 seed Flavio Cobolli, will be the first all-Italian singles semifinal at a Grand Slam event in the Open era.

Rather than worry that the test will prove too physical, Colangelo and Arnaldi prefer to keep dreaming that they can beat the odds.

“You start winning, you win matches that you almost lose, and then something happens,” he says. “If you have his level, then it's easy to change. He started to play better, to move better – it’s tennis, it can be like this.”