Stephen Robinson is adamant St Mirren should have been awarded a penalty under the Tynecastle floodlights.
But he admits his Buddies didn't defend well enough to merit making the Scottish Cup semi-finals on Saturday night.
The Saints were uncharacteristically sloppy at the back in Gorgie, shipping four goals as Hearts booked a coveted spot at Hampden Park next month.
While Robinson insists his side should have had a chance to score from the spot when Greg Kiltie was brought down in the box, the manager knows his side need to tighten up at the back going forward.
Robinson said: "Ultimately if you lose four goals you're going to lose the game, but I don't think 4-2 tells the whole story really.
"We dominated the ball for large spells of the game and caused them a lot of problems.
"We scored two wonder goals, but we didn't hold the 2-2 long enough and didn't do our defensive duties right.
"We didn't have that ownership of the game that would have allowed the crowd to get on top of them a little bit.
"There's a penalty decision that should have gone our way in the first half. I've seen it back and it's quite blatant.
"Unfortunately these things you can't control, and ultimately we ran out of steam in the last 15 minutes."
