Ian McCall insists Ayr's Premiership hopes are far from dead - despite facing a play-off mountain.
United's 3-1 defeat to clinical Inverness Caley leaves the Honest Men with it all to do in the Highlands on Saturday.
But McCall said: "We'll go up there and have a right go - and if we score the first goal then who knows.
"The disappointment for us is that in a big game like this, the officials have got two big decisions wrong.
"Their second goal was a yard offside - and I mean a yard - and the penalty was just never a penalty.
"But you get them wrong and we all make mistakes."
Ayr were on the wrong end of two dubious calls as Caley put themselves in the box seat to face Dundee United in the semi finals.
The hosts had started well with Declan McDaid looking a constant menace down the left but Ayr couldn't turn their early edge into clearcut chances.
And they were made to pay when Caley hit the front against the run of play when Charlie Trafford headed home a Joe Chalmers corner.
The lead was doubled shortly after the break when Jordan White, who appeared to be offside, lifted the ball over Ayr keeper Ross Doohan to put the visitors in control.
United hit back with a Michael Rose header as he thundered Luke McCowan's corner home from six yards.
But they were stung again when Liam Polworth was tugged in the box and a penalty was awarded, with White stepping up to make it 3-1.
Inverness boss John Robertson said: "The tie is far from over because we know what Ayr are capable of.
"This is the side who dismantled Dundee United 5-0 so we'll have to be ready."
