Plzen level late with Milan
Milan striker Alexandre Pato fired the opener in the 47th minute and set up strike partner Robinho for the second as the Rossoneri continued their strong run of form. The Serie A club looked to be cruising towards a win, but David Bystron pulled one back for Plzen in the 89th minute and Michal Duris equalised from close range in injury time.
Milan had already secured progression into the knockout stages behind Barcelona and approached tonight's game in buoyant mood after they extended their unbeaten run in the domestic league to eight games following the 2-0 win over Genoa at the weekend.
The draw means Plzen have guaranteed UEFA Europa League football in the new year as BATE Borisov were beaten 4-0 by Barcelona in the other game, meaning the Czech side finished third in Group H.
"There's anger because this is the Champions League, we led 2-0 right to the end and we had chances to go 3-0 up," AC Milan coach Massimiliano Allegri said. "The whole defence was new, they did well. In the first half we did really well, especially in attack.
"In the second half we did well, scored goals and had chances for 3-0, but we didn't take them and we paid for that."
For Plzen coach Pavel Vrba it was an ideal way to celebrate his 48th birthday. "In the first half we didn't let Milan play, we had at least four chances in which we should have shown more calm," Vrba said. "Unfortunately, we totally failed at the beginning of the second half, we conceded two very cheap goals in three minutes.
Both sides had good chances in the first half but neither could break the deadlock until Milan's quickfire double strike after the break. Pato's shot went wide in the ninth minute before Plzen midfielder Vaclav Pilar blasted his shot over the bar from Pavel Horvath's corner.
Clarence Seedorf delivered a testing corner for Milan just before the half-hour, but Pilar made a calm clearance at the near post to deny the Serie A side. Mattia De Sciglio then blasted over the bar from 30 yards before Plzen missed a chance at the other end when Milan goalkeeper Marco Amelia caught Frantisek Rajtoral's strike.
Seedorf also fired over the bar from range before Pilar and Milan Petrzela were both off target for the home side as the first half drew to a close.
Pato scored two minutes into the second half when he linked up with Robinho before rounding the keeper and sliding the ball into the open net. The strike partners reversed roles just a minute later when Pato set up Robinho for the second to give Milan a comfortable lead.
Robinho beat Plzen goalkeeper Marek Cech with a strike from the middle of the area which flew into the top of the net. Milan were now dominating the clash, with Seedorf forcing a save from Cech with another 25-yard effort before Pato struck the post from the right of the box before Cech managed to save his follow-up effort.
Plzen midfielder Petrzela hit the post in the 57th minute before Rajtoral's long-range effort missed the target soon after.
The home side finally got onto the scoreboard with one minute remaining thanks to Bystron's close-range strike. And Duris's equaliser two minutes into injury time completed the comeback as the Czech side secured a place in the Europa League round of 32.