Danish under-21 defender Mikkel was signed on 15 May 2002 for a fee of £750,000 from the Danish club AS Copenhagen. He was the fourth Dane to sign for City in less than a year, with Peter Schmeichel, Niclas Jensen and Kevin Stuhr Ellegaard in at City already. Bischoff's capture was part of a move to strengthen the team's prospects for the future although he was unable to make an impression as he underwent a hernia operation after making his one and only appearance for City against Blackburn in September 2002. He was under the knife again in the summer of 2003 after picking up a foot injury playing for Denmark under-21s.
Things didn't get much better for Bischoff during the 2003/04 campaign. He returned for one game only - making an appearance in the starting line-up for the second-leg UEFA Cup victory over TNS in August. He picked up an injury and was ruled out until the new year. Bischoff then recovered and returned but in the reserves, sustained another injury and was out again until the final week of the season when he returned to training. Still relatively young, the Dane will be looking to put his injury nightmare behind him and concentrate on getting in the squad and forcing his way into Kevin Keegan's plans for the 2004/05 campaign.
At the end of September 2004, Mikkel joined Championship side Wolverhampton Wanderers on a month-long loan deal, in order to gain some valuable first team experience