The Reds were made to work hard for the win with the Mariners looking the more likely at times during the clash, pushing Adelaide right until the end.

United will now face minor premier Melbourne City at Hindmarsh Stadium on Wednesday night before the second leg in Melbourne on Sunday.

Coach Carl Veart heaped praise on his side, saying he was always comfortable with how the game unfolded.

“It was a bit of a stretched game, that’s the way Central Coast play,” he said.

“They push a lot of numbers forward and I think we limited the opportunities they had to get in behind us.

“It’s finals football, it’s always on a knife’s edge, it can go either way and our boys were tremendous.”

Adelaide attacked straight from the kick-off but once the Mariners settled, they gained control of the match and pushed the Reds back.

United eventually worked their way back into the contest and the two sides traded blows before the Reds broke the deadlock on 26 minutes.

A strong interception from Aleksandar Popovic saw the young stopper storm out defence before supplying a through ball to Craig Goodwin.

The Reds winger latched onto the pass, after it had wrong-footed Central Coast defender Cameron Windust, and slid his first-time effort past the on-rushing goalkeeper Mark Birighitti.

United doubled their advantage on 66 minutes after a well-worked passage.

Isaias played a first-time, long ball out wide on the left to Goodwin, who whipped in a perfect cross for Kusini Yengi to side-foot home from close range.

The Mariners pulled one back just four minutes later thanks to substitute Storm Roux, and Central Coast pushed for an equaliser but in stoppage time the Reds scored a third courtesy of Bernardo.

It was Isaias who was once again supplying the pass out from midfield with Bernardo’s first touch taking it past his defender before driving towards goal and firing low and hard from the outside of the area, wrong-footing Birighitti.