Jannik Sinner held onto his world No 1 ranking ahead of his return from a three-month doping ban, but the Italian does not expect his comeback to be as smooth when he takes to the court again at the Rome Masters next month.
Sinner has not played since winning the Australian Open at the start of the season and accepted a ban in February following a deal with the World Anti-Doping Agency, which had challenged a tribunal's decision to clear him after two positive tests.
The 23-year-old was allowed to return to training on 13 April and his suspension will end on 4 May, before his competitive return at the Italian Open, which gets underway three days later.
Sinner, who spent time building fitness mindful of the French Open starting on 25 May, was assured of retaining the top ranking for his home tournament after his closest challenger, Alexander Zverev, crashed to an early defeat in Monte Carlo.
"We're training very hard. Hopefully, we'll get some momentum going again ahead of the clay season. It certainly won't be easy for me," Sinner told broadcaster ORF Sudtirol.
"The first games will be really difficult. But hopefully I'll be able to get back into the rhythm and then we'll see how it goes."
Sinner, who trained with Britain's world No 6 Jack Draper at the Tennis Club de Beaulieu in France recently, said there were plenty of positives from his enforced absence from the tour.
"I think at the beginning of the three months, it was quite nice," Sinner added.
"A bit of time away from all the grind, I spent time with family, with friends. I was doing new things and getting to know myself better, finding out where I stand.
"I think it helped me a lot."