Kwabena Appiah headed the hosts into a 1-0 lead at Central Coast Stadium but a poor period immediately after half-time allowed Adelaide to take control.

“In the first half, for me, we should have been two or three goals up. We played some great stuff,” Montgomery told Fox Sports.

“In the second half we concede a sloppy equaliser and then it’s not acceptable [to concede from] two set-pieces. There are too many bodies standing still.

“We’ve let ourselves down today. Massively disappointing because today was a game we needed to win.”

Roy O’Donovan’s 90th minute penalty wasn’t enough to inspire a late comeback, leaving Central Coast last on the ladder after 24 matches.

The Mariners face a fight to avoid the wooden spot with away dates against Brisbane Roar and Melbourne Victory either side of an F3 Derby still to come.

“We’ve got to win three games and give ourselves a bit of pride,” Montgomery said.

“There have been massive steps forward this season but in terms of results we’ve still got a long way to go.

“We’ve got to go out in the last three games, try to get some points on the board and finish higher up than we did last season.”