Wellens began his career at Manchester United before signing for Blackpool in 2000, where he went on to win promotion from League Two via the playoffs in 2001. In 2005, he left them to move to Lancashire rivals Oldham Athletic where he made 87 appearances in two seasons at the club. After his spell at Oldham, Wellens made his successful move to Doncaster Rovers in the summer of 2007 where he became an instant fans' favorite, helping the club rise into the Championship for the first time in 50 years. His time at Doncaster came to an end in 2009 after he had helped the club to consolidate their Championship position as he moved to Leicester City. In his time in the Midlands, Wellens made 129 appearances, scoring four goals, and winning the club's Player of the Year in 2011. After a short loan spell with Ipswich Town, Wellens rejoined Doncaster in 2013.