Complex sentence: He made his senior debut on 19 September 2009 on loan at Colchester United against Hartlepool, and remained with the U's for the rest of the 2009--10 season.
Split into simpler sentences: He made his senior debut on 19 September 2009 on loan at Colchester United against Hartlepool. He will remain with the U's to the end of the 2009--10 season.