Fognini even admitted he preferred watching Federer play a few years ago, and cast doubt over whether the 40-year-old could return to the same level.
The Swiss star has barely played in the last two years, undergoing three surgeries for a troublesome right knee injury, and is still uncertain on when he will return.
“I would pay to see Roger like in the old days. I don’t know if we will see him like before,” the nine-time title winner said.
“I love Federer. Everything seems easy for him, but it’s not like that.”