The midfielder, on loan at Sheffield United last season, found the target at the Absa Stadium in the 23rd minute.
Martin reacted quickly after Fraizer Campbell flicked the ball on, the 21-year-old applying a cool finish.
United boss Sir Alex Ferguson told MUTV: "I'm satisfied with the result. Some of the football we played in the first half hour was very satisfying: there was a lot of vision, movement and quick passing in our game, and we didn't dwell on the ball.
"The Pirates were very aggressive in terms of pressing the ball and we had to be quick on it, which can only help us.
"After 30 minutes we lost our momentum a little bit, which happens with young players. They start to lose concentration. Defensively we were caught one or two times on the counter-attack but they had a lot of pace, although they weren't great finishers."
Ferguson had words of encouragement for Martin and Chris Eagles and is confident the young midfield duo can fulfil their potential by playing more regularly.
"Some of the players have not had enough football at this level, of course," the Reds boss continued. "Eagles and Martin have been out on loan, Martin got injured at Sheffield United and needs a lot of football, but there's a lot of talent there, as is the case with Eagles.
"Hopefully they can start to get regular football at a good level because to fulfil their talent and promise they really have to be playing football."