Jose Mourinho's football club Inter Milan has said he didn't assault a fan after side's Champions League defeat on Wednesday to Manchester United.
Mourinho has been accused of attacking a supporter after watching Milan lose 2-0 to Manchester United, and crash out of the competition.
Officers said the fan didn't report any injuries, and hadn't needed treatment.
But they are investigating the complaint, and have asked for CCTV footage of the area on the night.
The statement from Inter Milan said that after the game Mourinho gave some interviews, signed autographs, watched the penalty shoot-out between Roma and Arsenal and met up with Sir Alex Ferguson.
Inter added: "After giving the last interview to Inter Channel, he entered the team bus that was parked outside the dressing rooms and hence it was a very calm post-game experience."
The Champions League tie took place at Old Trafford, Manchester United's home ground.
Inter Milan lost the Champions League tie with Man United
United made it through to the quarter-finals and knocked Inter out of the competition, after Nemanja Vidic and Cristiano Ronaldo scored a goal each.
After the match the fan is said to have chanted, "You're going home, you're going home," to Mourinho, a former Chelsea manager.
The fan later reported the attack which is said to have happened outside the stadium, at a police station near Old Trafford.
A Greater Manchester Police spokesman said: "Just before midnight on Wednesday 11 March 2009 a man reported he'd been punched in the face outside Old Trafford.
"Police are investigating this common assault allegation. Inquiries are ongoing."