The Serie A outfit started off brightly but experienced a nervy first half after letting the Russian outfit back into the contest.
Sports Mole takes a look back at the 90 minutes of action from the Group C clash.
Zenit St. Petersburg
On Target: 11
On Target: 7
Was the result fair?
For large parts of the match, you would have to argue that the result was slightly unfair to Zenit considering their first-half comeback. From the statistics the home side had the majority of possession and more shots on goal than their Italian opponents, but the Serie A side were able to defend when it mattered.
Zenit St. Petersburg's performance
The Russian outfit looked lost in the middle of the park for the first 20 minutes but they soon grew into the game and controlled the contest, which enabled them to get star striker Hulk into good positions to threaten. Despite coming from 2-0 down to equalise, the home side did let Milan get back into match, which was costly.
AC Milan's performance
Milan looked like they were going to dominate after going two goals to the good in the first half an hour but they slowly lost their attacking threat and were largely kept in the game by their goalkeeper Christian Abbiati. Despite a tough test, the seven-times champions were able to defend in numbers and take their chances when they came about.
German official Felix Brych had an inconsistent game. While the referee let the game flow quite well, the German was quick to caution players and ended up issuing seven yellow cards over the course of 90 minutes. Brych also waved away two penalty claims - one from either side - which in hindsight should have been given.
Sports Mole's man of the match
Milan goalkeeper Abbiati kept his side in the game in the first half by executing some vital saves. The Serie A keeper was under hoards of pressure from the home team and while the shot-stopper let in two goals, he also prevented Zenit from grabbing a late equaliser.
This would have to go to Tomas Hubocan, who's own goal gave Milan the vital three points in Group C. While the shot coming in was difficult to deal with, Hubocan's desire to stop Giampaolo Pazzini from scoring backfired as the ball bounced off him and into his own net.
Zenit St. Petersburg: Zenit will hope to regain their home form and pick up some much-needed points when they welcome Anderlecht on October 24.
AC Milan: The Italians are away again when they travel to Malaga in three weeks' time as they hope to stay at the top of the group.