City took the lead thanks to goals from Vincent Kompany and Ilkay Gundogan but Paul Pogba's brace brought United level before Chris Smalling volleyed home to spoil Guardiola and City's hopes of securing the Premier League title.
Lukaku didn't get on the scoresheet but Guardiola revealed himself to be a fan of the Belgium international after the game, hailing Lukaku as "world class".
He said, as quoted by Manchester Evening News:
“I saw him when he played for Everton with my friend Ronald Koeman - he punished us here in the Etihad Stadium and he punished us in Goodison Park.
“He’s fast, going to the channels, he helps to keep the ball and helps to make the movement for the other guys.
Pep Guardiola on Lukaku: “I would never say that he’s is not able to play for me. He’s 24 and has 100 PL goals. So not bad, first of all. He’s fast, going into the channels, helps to hold the ball up & helps the other guys to make their moves. He’s top. A world class player.” pic.twitter.com/bfL7ZWgu8c— Kristof Terreur 📰 (@HLNinEngeland) April 7, 2018
When asked whether Lukaku could adapt to his style of play, Guardiola responded: “All the good players adapt to all the styles in the world, not just mine. No, no, no. I would not say that (he could not adapt.)
“I would never say that Lukaku is not able to play with me or all the managers in the world.