A star of the academy, with whom he played in two consecutive Grand Final wins with, he broke into the first team at the end of 2002 after a loan spell with Warrington.

The following season Mathers became a first team regular and his form in 2004 was such that the Leeds club allowed the former Wigan Warriors "star Gary Connolly to depart.

By 2005 Mathers was promoted to the number one shirt and was one of the first names on the team sheet,[citation needed] only missing one match all season.

One of the highlights of the years was when he helped the team to victory in the 2005 World Club Challenge when he scored a try against the Canterbury-Bankstown Bulldogs at his beloved[citation needed] Elland Road, Leeds.

Mathers played five rounds and appeared to be gaining confidence and good form until he ruptured the anterior cruciate ligament in his right knee.

Mathers scored a try in a 47–28 win at Harlequins on his Super League début for Wigan but was sent off for the first time in his career in Round 5 against Warrington for a high tackle on Matt King, for which he received a three-match ban.

However, Mathers was red-carded again in Round 25 for leading with an elbow as he attempted to fend off Wakefield's Jason Demetriou, although Wigan still won 32–22 to secure a play-off place.

Mathers was sin-binned during Wigan's opening game of 2009's Super League XIV for a trip on Wakefield wing Dave Halley.

On 7 August, Kingstone Press Championship side London Broncos announced the signing of Mathers on a two-year deal starting from 2015.