Thiago Silva headed in a stoppage-time equaliser to earn AC Milan a draw against Barcelona at the Nou Camp.
Milan had also started the match in stunning fashion with Alexandre Pato netting in the opening 30 seconds but Barca turned the game around and looked to be on course to claim the win thanks to goals from Pedro Rodriguez and David Villa.
However, Pep Guardiola's men could not find a third goal to wrap the tie up and they were stunned two minutes into injury time when Thiago Silva powered home Clarence Seedorf's corner to salvage a point for seven-time European champions Milan.
The Italian gave his analysis of the match to UEFA.com, saying: "We started very well, then later in the game we were forced to defend because Barcelona had possession and it was difficult to press them.
"However, we did not afford them great chances to score and we also had a few opportunities to get a second on the counterattack in the first half."
While Allegri believes his side could have played better, the manager believes that it was good that Milan continued to press for an equaliser even late in the game, and were rewarded by Silva's goal as a result.
"We could have played better after Barcelona took the lead but I'm happy because the team didn't collapse, always remaining in the game until the late equaliser", the Italian beamed.
"Our plan was not to allow them a numerical advantage in midfield by pressing when we didn't have to. We also defended well when they were trying to pass in behind our defensive line.
"We have room for improvement but I'm happy with the way every player helped each other today", Allegri concluded.
Speaking on the club's official website later, he said: "This result is worth a draw. Nothing more, nothing less.
"It was an important game and we were not at our best physically.
"But we gave little away to Barcelona and I believe the 2-2 draw is a good reward for us.
"One thing I did like was that when we were 2-1 down, my team did not lose its focus.
"We played the game we wanted to play, following our game plan."
Allegri will be hoping to recover Massimo Ambrosini and Kevin-Prince Boateng for Sunday's match at Napoli.
Both players got hurt during the game at the Nou Camp, with Ambrosini sustaining a shoulder injury and Boateng sidelined with a muscular problem.
"We will evaluate Boateng and Ambrosini's condition tomorrow [Thursday]," said Allegri.
AC Milan will next take on Viktoria Plzen on Wed, 28 Sept, at the San Siro in their next European encounter.