Guardiola and Ronaldo have done battle against each other several times over the years and the Spaniard was close to securing the services of the Portuguese from Juventus at the start of this season but Manchester United swooped in at the last minute.
Nonetheless, Guardiola is grateful for what the 37-year-old five-time Ballon D’or winner has given the game, alongside longtime nemesis Lionel Messi.
"One of the greatest in the last 15 years alongside Messi," Guardiola told a pre-match press conference on Friday when asked on Ronaldo. "We aren't going to see it again.
"When you achieve these things, you're under scrutiny every day. He was too good and as a finisher, exceptional - a top player. It has [been] a joy to watch in these years.
"We have to exploit our game and strength to avoid him close to the ball. We have to control him. One of the greatest - a goalscoring machine.
"He is so strong mentally. He handles this pressure without a problem, [and] lives with expectation through his career in a positive way."
Ronaldo has made 30 appearances and scored 15 goals for Manchester United this season.
