Zdenek Zlamal has apologised to Hearts fans after his blunder allowed Celtic to take a 2-0 lead in the Edinburgh side's League Cup semi-final defeat.
Zlamal fumbled Ryan Christie's shot and could only scramble the ball clear to James Forrest, who slotted home.
"The second goal was mine," the goalkeeper said after the 3-0 loss.
"I think Michael Smith touched it a little bit, but I have to catch it. I have to say sorry to all fans and to everybody."
Hearts lost captain Steven Naismith to a knee problem in the opening minutes and the on-loan Norwich City forward is now a doubt for Wednesday's Scottish Premiership derby at home to Hibernian.
Peter Haring, who performed well again in midfield, and Clevid Dikomana, who impressed in defence, are also struggling after picking up knocks against the cup holders.
"We have to forget this game," Zlamal said. "Next game, we play against Hibs and it's a very important game for everybody. We keep going.
"We have a lot of injured players, so it's not good, but we have other good players who are waiting for a chance and now they can show it."
Hearts made the short trip to Murrayfield as Premiership leaders, five points ahead of Kilmarnock and a further one above Celtic.
However, the reigning Scottish champions could have won by a wider margin had it not been for a couple of superb saves from Zlamal.
"We are very disappointed," the Czech goalkeeper added. "We felt that we had a big chance to be in the final.
"I was so focused on the game and mistakes are part of football. It's normal, everybody makes mistakes.
"I was focused on trying not to concede another goal, but Celtic were much better than us after the second goal."