Ian Murray lamented Airdrie's late collapse against Cove Rangers after they were knocked off top spot in League One.
And the New Broomfield boss says they missed a "huge opportunity".
Rivals Queen's Park suffered a shock defeat at Peterhead to drop to fourth place in the table, while Montrose's win over Falkirk pulled them up to third.
But instead of increasing their advantage at the top of the table, the Diamonds are now two points adrift of new leaders Cove after goals from Mitch Megginson and Fraser Fyvie gave the visitors all three points in North Lanarkshire.
The Diamonds switched off late on and Cove struck twice in three minutes to claim victory in a game that seemed to have a stalemate written all over it.
And gutted Murray said: "It was very frustrating for us.
“We stated the game poorly. Cove started better than us in the first 20 minutes and we kind of took over towards the end of the half.
“The second half we started well and dominated for 20 minutes.
“But to lose the goal when we did in this type of game, it’s very difficult.
“There’s huge frustration in the way we conceded the [first] goal. We had so many opportunities within the minute leading up to it to eradicate the danger, but we didn’t do that.
“A cross ball into the box has got to be dealt with better, it’s as simple as that. You need to get closer to your man.
“It’s a huge missed opportunity for us, regardless of what went on elsewhere, because it’s about winning your home games.
“As the home team I didn’t think we deserved to win the game. A draw might have been fair but we have to better than that.
“I’m hugely disappointed, and the players are as well, with the manner we’ve lost the match."
Cove skipper Megginson popped up 11 minutes from time to head in off the post from Blair Yule’s cross, before substitute Fyvie poked home the clincher from Harry Milne’s delivery.
Airdrie did have chances, with the best chance falling to Dylan Easton in the second half when Cove keeper Stuart McKenzie gifted him the ball on the edge of the box, but the shot-stopper redeemed himself with a good save.
Murray, though, felt his side didn't create enough to deserve a victory after a run of five wins in their previous six games.
It was their second defeat to Cove in two meetings this term and Murray said: "We didn’t create enough and our movement wasn’t good enough.
“We were a bit tentative all over the park, with and without the ball, but the manner we lost the goals is the real frustration.
“Small things in games separate teams at the end of the day and we didn’t deal with that very well.
“We know the standards need to better because if you want to go and challenge in leagues or try and win leagues, you need to be consistent against the good teams - and Cove are a good team."
Follow Lanarkshire Live Sport on Twitter via @LanLiveSport, like us on Facebook or find us on Instagram for the latest sports news, pictures and video.
