The Old Trafford outfit followed Diouf for two years before signing him from Norwegian club Molde for a fee in the region of £4m in the summer of 2009.
The Senegal international was sent back to Molde on loan until the end of the Norwegian season and then linked up with his new Manchester United team-mates in January 2010.
Recalling his first day with the Red Devils, Diouf has admitted that he could not believe that he was seeing the stars that he was used to watching on television right before him.
The 33-year-old explained that he could not believe he was sharing the dressing room with the likes of Wayne Rooney, Paul Scholes, Dimitar Berbatov and Ryan Giggs and labelled the experience an unforgettable one.
“I can’t forget the first day I walked into the dressing room“, Diouf, now on the books at Hatyaspor, told Turkish daily Hurriyet.
“When I saw people coming in, it occurred to me that I saw those people playing football on TV on Sundays.
“I couldn’t believe it when I was in the dressing room with them.
“I asked myself if I was really here.
“‘Is it really Rooney, Scholes, Berbatov or Giggs that I am seeing?’ I was asking myself.
“When I joined that team, everyone was helping me reach my highest level and sharing their experiences with me.
“It was an excellent experience.“
Diouf went on to make nine senior appearances for Manchester United, contributing two goals, before leaving the club for Hannover in January 2012.