Match sponsorship dedicated to: Hestia Stoves and Fireplaces
It was an encouraging start for Ballynahinch United when Lee Maxwell broke free but his left-footed attempt sailed over the bar.
United had two more early opportunities to break the deadlock but failed to do so.
But it was the away side who took the lead but Ballynahinch equalised through Louis Boyd-Wisoner, for his first goal for the club.
Ballynahinch were forced into a change when Chris Coleman was subbed after an injury. Chris was making his 50th first team apperance for the club. On the other end of the scale, Tom Nelson made his debut for the club.
The home side found themselves behind by the end of the half, with Castlewellan bagging two more.
By the end of the game, the floodgates had opened at The Millbridge, despite a missed penalty by a Castlewellan forward.
Line up: Stefan Graham [C], Tom Nelson, Simon Johnston, David Osborne, Chris Coleman (John McMenamin), Gavin Crawford, Kyle Spindlow, Glenn Moffett, Louis Boyd, Ross Murray (Charlie Parkinson) Lee Maxwell (Bradley Hamilton).
Ballynahinch United will return to action on Thursday 14 August against Bloomfield at Houston Park. Kick off at 7pm.
The Swifts kick off their campaign with a home tie in the KitRoom Cup on Saturday, against Celtic Bhoys Academy.