Sinner took little more than an hour to sweep aside Madrid champion Ruud on centre court at the Foro Italico, winning 6-0, 6-1 and storming into the Rome semi-finals.
"It's as near as perfect that I witnessed, at least as a player, playing someone, so just got to give it to him," Ruud told reporters.
"Everything else that came out of his racket... feels like a hundred miles an hour plus, every single shot, on the forearm, from the backhand, and even on my shots that I feel at times are pretty heavy, it comes back like just firing.
"He was just everywhere... It's just like playing a wall that you know shoots hundred-mile-an-hour balls at you all the time."
Ruud drew the loudest cheer of the night when he held his serve to win his only game, and he insisted that even he enjoyed watching Sinner's dominant performance.
"It doesn't feel so bad, honestly. I think it was more fun than anything," said Ruud.
"You just look at the guy and say 'wow this is kind of next-level shit', excuse my language. I don't know what else to say, it was almost fun to witness.
"I was there ready to play, but he was just even readier."
Sinner will face Tommy Paul, a 7-6, 6-3 winner over Hubert Hurkacz in the day's first match, in the last four evening as he continues his comeback from a three-month doping ban.
The world number one could yet play rival Carlos Alcaraz in a blockbuster final between tennis' leading men, but he said he is not complacent about his chances on Friday.
"There's not really a lot to say, I'm very happy, but things can change from one moment to the next," said Sinner.
"Tomorrow we have another player. I played against him at the US Open, and it was a very difficult match (won in straight sets). Let's see what I can do tomorrow."