Zaha, who is currently on loan at Cardiff from United, was replaced after 62 minutes and a vocal minority of the Bluebirds' supporters voiced their displeasure at his performance as he left the field.
But his inconsistent display sums up his career to date following his departure from Crystal Palace last summer.
He failed to win a spot in David Moyes's plans after spending the preseason with United, and was allowed to join Cardiff on loan on deadline day in the January transfer window.
Former-United striker Ole Gunnar Solskjaer, who now manages Cardiff, handed Zaha his first start against his former club at the weekend but Zaha struggled to influence the game and was hauled off on the hour mark.
But Mariappa believes Zaha just needs time to show his quality in the Premier League.
Speaking to the Croydon Advertiser, Mariappa said: "I didn't play with him last season so I don't know what he's like as a character.
"I'm sure once he gets a run of games and playing week in, week out, his form will come good."