Celtic crashed out of Europe after surrendering the lead to Aalborg in their Champions League game here last night.
They had dominated from the first whistle and there was no surprise when midfielder Barry Robson put them ahead in the 52nd minute with a diving header.
Gordon Strachan's side looked to be on their way to winning their first away tie in the group stages of the competition at the 18th attempt, but in the 72nd minute, and out of the blue, Caca drew his side level with a drive from 25 yards which deflected off captain Stephen McManus before the ball looped over goalkeeper Artur Boruc.
When Gary Caldwell put through his own goal three minutes from time the Scottish side's misery was complete and they do not even have the consolation of a Uefa Cup place to look forward to in the new year.
"I just hope it's a bad dream, to come here and have so many players playing well," Strachan said afterwards. "At 1-0 I thought, 'Tonight's the night – we're going to get this away victory'. I couldn't see any threat at all.
"We created enough tonight to finish the tie off," he added. "We weren't good enough to take them so we blame ourselves. It was there for us but our inability to keep a clean sheet has been our downfall and until we get that sorted nights like tonight are possible."
Neither side could entirely impose themselves in the first half but Celtic were soon in control after the break and took the lead when Robson scored. But 20 minutes later the visitors were stunned when Caca replied. The game changed on that incident.
Celtic's search for that elusive away win in Europe continues while the post-mortem begins.
Aalborg (4-4-2): Zaza; Bogelund, Olfers, Jakobsen, Pedersen (Kristensen, 81); Caca, Augustinussen, Johansson, Risgaard; Enevoldsen (Due, 70), Curth (Saganowski, 70). Substitutes not used: K Nielsen (gk), Nomvethe, Braemer, Sorensen.
Celtic (4-4-2): Boruc; Hinkel, Caldwell, McManus, Wilson (Maloney, 89); Nakamura, S Brown, Robson, Loovens; Samaras (Sheridan, 69), McDonald. Substitutes not used: M Brown (gk), Naylor, Hartley, O'Dea, Caddis.
Referee: K Plautz (Austria).