Complex sentence: In his first game playing for the Terriers, however, he picked up an injury and had to return for treatment to Old Trafford, where he would remain until 2003, but often sidelined by injury and playing mainly in the reserve team.
Split into simpler sentences: In his first game playing for the Terriers though he unfortunately picked up an injury and had to return for treatment to Old Trafford. May remained at Old Trafford until 2003, but was often sidelined by injury and played mainly in the reserve team.