Manchester City finished with Kyle Walker in goal as its progression to the Champions League knockout stages was stalled by Atalanta in a dramatic 1-1 draw.
Raheem Sterling's seventh-minute goal looked set to be paving the way for another dominant display from the Premier League champion, which thrashed Atalanta 5-1 in the reverse fixture and wanted a win to guarantee its place in the last 16.
However, Gabriel Jesus' dreadful penalty miss and the half-time substitution of goalkeeper Ederson – who reportedly had a minor injury – handed Atalanta hope, with Mario Pasalic then heading in their equaliser.
A red card for Ederson's replacement, Claudio Bravo, caused mayhem in the closing stages, with Walker, after a long delay, brought on to take his place in net, and the emergency goalkeeper held his nerve as City held firm to claim a point.
Hans Hateboer missed a great early chance for Atalanta, but it was City which took the lead when Sterling swept home at the culmination of a slick move.
City looked to have been gifted the chance to double its lead when referee Aleksey Kulbakov awarded a penalty for Rafael Toloi's foul on Sterling, only for VAR to rightly overturn the decision as initial contact came outside the box.
Chaos commenced from the resulting free-kick – Sterling's strike hit Josip Ilicic on the arm, with Kulbakov giving the penalty after checking with VAR.
Jesus' spot-kick let Atalanta off the hook, though, with the Brazil forward sending a dreadful attempt well wide of the left post.
Atalanta was level four minutes into the second half, as Bravo's first act was to collect the ball out of his own net after Pasalic powered in Alejandro Gomez's sensational cross.
Bravo's chaotic cameo was brought to an end in the 81st minute, with VAR backing up the referee's decision to send the goalkeeper off for a lunge on Ilicic after charging out of the penalty area.
Walker had to step up, but despite a nervy start when he fumbled Ruslan Malinovskiy's free-kick, the right-back was not severely tested as Atalanta failed to capitalise on City’s misfortune.
What does it mean? City's progress on ice, Atalanta have hope
Despite its difficulties in Milan, where Atalanta is playing its Champions League games, Pep Guardiola's side will surely ensure its progression at the next time of asking.
On November 26 it will have home advantage against Shakhtar Donetsk, which drew 3-3 with Dinamo Zagreb in an extraordinary encounter elsewhere in Group C on Wednesday. Meanwhile, Atalanta has their its point on the board, keeping its slim hopes of progression alive.
Atalanta talisman Gomez steps up
The experienced Gomez has been a staple of Atalanta's rise to prominence in Serie A, though he had failed to carry that form into the Champions League until Wednesday's outing. This time he turned on the style, providing a sublime assist for Pasalic's equaliser before he supplied the throughball which led to Bravo's dismissal.
Bravo makes history… for all the wrong reasons
City faces Liverpool next in what looks set to be a highly significant clash in the Premier League title race. Now Guardiola – who has already been fielding a makeshift defence – could well be without his first-choice goalkeeper at Anfield if Ederson cannot make it.
If Bravo is called upon, he will need to be levels above the display he put in at San Siro. The Chilean never looked settled, and his rush of blood to the head very nearly cost City dearly as he became the first substitute goalkeeper to be sent off in Champions League history.
Key Opta facts
- Manchester City failed to win a Champions League group stage game it was winning at half-time for just the second time, also doing so against CSKA Moscow in October 2014 (2-2).
- Atalanta picked up its first point in a Champions League match, having lost each of their first three matches in the competition.
- This was Pep Guardiola's 600th game in charge of a top-flight club in all competitions (W440 D95 L65).
- Six of Raheem Sterling's 19 Champions League goals have been against Italian sides, more than he has scored against opponents from any other country in the competition.
- Claudio Bravo became the first substitute goalkeeper to be sent off in Champions League history.
- Gabriel Jesus has missed three of his seven penalties taken in all competitions for Manchester City, though this was his first failure in the Champions League.
Title rivals City and Liverpool go head to head on Sunday in England's top-flight, while Atalanta travels to Sampdoria in Serie A on the same day.