The win was the Reds' second straight home win against the Big V - the first time they've achieved that feat since 2006 - and secures Adelaide a home final with one regular season match remaining.

Marco Kurz's side are now four points clear of Wellington Phoenix in fifth and in red-hot form heading into the finals, an achievement Marrone puts down to their renewed focus on width.

"When we've played them in the past we've always made silly mistakes," Marrone said.

"We've tried to play out through the middle and they've cut it out and gone forward. Then you're 1-0 down, chasing the game and it's disappointing.

"We didn't want that to happen at home."

George Blackwood also added another element to United, scoring a driven header in the second half. Marrone implied that Adelaide are still looking to improve.

"In the first half we were playing without much risk," he said.

"As the game progressed I thought we did a little bit better [on the ball]. Still not at our best but it was good enough to get the points."