Derby player-coach Wayne Rooney says Park Ji-sung was a crucial part of Manchester United.

Rooney believes Park was "just as important" as Cristiano Ronaldo to United's success because he embodied the strong team ethic of Sir Alex Ferguson's side.

Writing in The Sunday Times, Rooney said: "It's crazy but if you mentioned Cristiano Ronaldo to a 12-year-old, they would immediately say, 'Yeah, he was a brilliant player for Manchester United', but if you said 'Park Ji-Sung' they may not know who he was.

"Yet all of us who played with Park know he was almost as important to our success.

"That's because of what Park gave to the collective and I want to talk about teams. They - not stars - are the most important thing in sport."

Rooney recalls United's last-16 encounter with AC Milan in 2010 as an example, with Park's dogged man marking of dangerman Pirlo a key reason why they won the tie 7-2 on aggregate.

"I remember Fergie's team talk before playing AC Milan. He literally said to Park: 'Your job today is not about touching the ball, it's not about making passes, your job is Pirlo. That's all: Pirlo'," Rooney said.

"I think Pirlo barely had 40 passes in that game, and 95 per cent were backwards because Park was so unbelievable at carrying out his orders."