On 26 September 2003, he fought future world champion David Haye at cruiserweight.
[3] A fight against another future world champion came against Lucian Bute on 16 May 2006, which ended in a twelve-round unanimous decision loss for Mock.
On 3 November 2006, Mock won his first major regional championship—the vacant European Union super-middleweight title—when he defeated Franck Mezaache via fifth-round corner stoppage.
[4] Having vacated the title after one defence, Mock won it twice more on 14 March 2008 and 30 January 2010, against Mouhamed Ali Ndiaye and Giovanni De Carolis respectively.
In 2016, Mock had his busiest ever year as a professional, having six fights in Denmark and winning each time.