Rovers completed the signing of the Northern Ireland defender on 3rd January 2013 following his release by Tranmere Rovers where he initially joined the club on a short term deal until June 30th.
He formed an impressive central defensive partnership with Tom Parkes and proved himself to be popular with supporters. He was offered, and accepted, a new permanent contract in the summer of 2013.
The former Northern Ireland U-21 captain began his career at Wolverhampton Wanderers, and his time at Molineux included a loan spell with Bradford City.
On his release from Wolves he signed for his local side, Derry City.
In January 2007 he joined Partick Thistle and scored once in 15 league appearances for the Scottish outfit before returning to Derry City in August 2007 and joined Lisburn Distillery, on a short term contract, in late 2009.
A third spell with Derry City followed before a move to Tranmere Rovers in January 2011and he went on to score once on 41 league appearances for the team from the Wirral.
A one month loan spell at Scunthorpe, in November/December 2012 saw him play three league games for The Iron, and he was released by Tranmere on his return to Prenton Park.
Mark scored his first goal for the club in last season’s JPT tie against Bristol City at Ashton Gate, on 4th September 2013.
One of Darrell Clarke’s first actions, after taking over as manager with eight games of the 2013/14 season remaining, was to hand Mark the captain’s armband.
Mark showed he is no slouch between the posts last season when he took over from the injured Steve Mildenhall in goal during our away game at Wrexham and he skippered the side in the Promotion Play Off Final at Wembley.
McChrystal made 24 appearances for Darrell Clarke's side last season and was vitally important to the final push for promotion and Chairman Steve Hamer is pleased to have secured the services of the club captain "It's another good news day for the Club, anyone who watched Marks contribution to the teams efforts during the promotion run in will recognise what a stalwart he was for the team.
"It's a tremendous boost to have quality and experience in your squad for what will be an exciting forthcoming season"