McChrystal began his career at Wolverhampton Wanderers[2] where he was one of a plethora of young players from Northern Ireland playing there.

His stay in the Irish League was short-lived however, and after just six games for the club, he picked up an injury in the quarter-final of the North-West Cup against Moyola Park which hastened his return to Derry City.

[2] He fought his way back into the team under Gavin Dykes and Peter Hutton but did not appear regularly during the reign of Stephen Kenny due to stiff competition in defence.

[7] He re-signed for Derry City in August 2007 after turning down a move to Glentoran[8] and being released by new Thistle manager Ian McCall.

[10] Unhappy with his limited first team chances after returning from a broken cheekbone and non-payment of wages, he negotiated an early release from his Derry contract in August 2009.

[15] Unhappy over non-payment of his wages by Lisburn[11] he rejoined Derry City for a third spell in January 2010, signing a one-year contract.

[24] On 4 September 2013, McChrystal scored his first, and what to be proved only, goal for the club with an equaliser as Rovers were defeated 2–1 by arch rivals Bristol City in the Football League Trophy First Round, the first meeting between the two in six years.

[28] Following their promotion back to League Two, McChrystal found first-team opportunities hard to come by at times with the defender making only ten appearances before February 2016.