Andy Roddick has predicted that clay will be the “toughest surface” for Ben Shelton as it neutralises the speed of his serve.

As tennis turns its focus to the clay season, Roddick spoke about why the 23-year-old may struggle in comparison to his colleagues.

In terms of the slams, the clay of the French has seen Shelton reach only as far as the fourth round while he has made at least the quarters in every other major.

As for titles, Shelton’s one on the ATP Tour so far has come on the hard court of the Canadian Open.

The American is currently competing in the Men’s Clay Court Championships in Houston but Roddick said on his podcast that one of Shelton’s most effective tools may prove less so on clay.

“I mean, that serve translates anywhere,” Roddick said. “When you could serve 140 and then kick it over someone’s head both ways. That tends to work.

“His ball flight on his forehand naturally has a lot of spin on it. You know, I think as the surfaces have become kind of more mono-surface, I think the entire thing is like, can Ben beat me today with his backhand? Which is tough because there’s only so many people that can neutralise the serve.

“On clay, people have more time to find space over there, right? Whereas, like, if his serve comes even quicker, you don’t have time to take a full swing and redirect.

“So, I think clay is just gonna be the toughest surface for him.”

Shelton started his clay season in impressive fashion as he registered 21 aces in a victory over Zhang Zhizhen, setting up a quarter final match against Thiago Agustín Tirante.

“It was my first match in almost a year on clay,” he said. “I didn’t feel that comfortable playing from the baseline yet, it’s just something that’s going to take time and take a few matches. I knew I had to be effective with my serve tonight and hit a few aces, and I’m happy that I did.”

Shelton is the No 1 seed for the tournament but has difficult opponents in the form of Tommy Paul and Frances Tiafoe ahead of him.