 On 23 December 2009, Diouf was granted a work permit making him available to play for Manchester United once the transfer window opened in January.After becoming eligible to play for Manchester United on 7 January 2010, Diouf was registered with the number 32 shirt worn previously by Carlos Tevez, and made his debut in a league match away to Birmingham City two days later; with the scores level at 1–1, Diouf came off the bench for Paul Scholes in the 81st minute, but he was unable to help break the deadlock and the match finished as a draw.Diouf made his home debut for United in a 3–0 win over Burnley on 16 January 2010, coming on as a 74th-minute substitute for Wayne Rooney.