Celtic required a stoppage-time penalty to rescue a point in their entertaining 3-3 draw with Dundee at Dens Park.
Brendan Rodgers acknowledged Celtic were "too passive" and "not aggressive enough" as they drew 3-3 with Dundee.
The Scottish Premiership leaders saw their three-match winning run come to an end as they were twice pegged back at Dens Park and then required a last-gasp leveller of their own.
Luke McCowan and Yang Hyun-jun saw efforts cancelled out by Oluwaseun Adewumi and a Cameron Carter-Vickers own-goal, before Aaron Donnelly headed the hosts in front in the 78th minute.
The Hoops managed to rescue themselves in the third minute of stoppage time through Arne Engels' penalty after Mohamad Sylla handled a Nicolas Kuhn shot.
While Rodgers praised the determination of his players in ensuring they did not leave the contest empty-handed, the Celtic head coach conceded they must do better.
"We had lots of control in the first 40 minutes, then we give away a needless goal from a counter attack. That gives them impetus," he said.
"I give credit to the players, they kept going. But for our standard, that second half has to be better. We were too passive, too slow. Just not aggressive enough.
"Tonight was about doing the basics well, and we did not do that well enough."
Dundee boss Tony Docherty was disappointed his side could not quite hold on for a first win over Celtic in almost 24 years, but was pleased with the way they held their own against the runaway leaders in testing circumstances.
"I'm immensely proud, but the overriding feeling is one of disappointment," he said. "I thought we did enough to win.
"I watched Celtic put on Kuhn, Engels, [Luis] Palma... I've asked Lyall Cameron to get off his sickbed to play; Finlay Robertson hasn't trained; Cesar Garza had to come off.
"To put in that level of performance against that opposition is bordering on heroic. We made a Champions League team wobble. We sensed it, we went for it and gave everything to win that match. I thought my players deserved that tonight."