United got off to the worst possible start, with goals from Mario Pasalic and Merih Demiral giving the visiting Italians a 2-0 lead inside the first half hour.
However, United came out of the half-time break looking like a completely different team, and Marcus Rashford’s early goal halved the deficit and had the home fans ecstatic.
Captain Harry Maguire then equalized for United with a smart finish 15 minutes from time, before a trademark Ronaldo leap and header with only eight minutes remaining secured a 3-2 win and capped another memorable Champions League night at Old Trafford.
It was critical for United to set the tone early on in order to gain the support of the crowd on a night that would be fraught with tension and potentially crucial to Ole Gunnar Solskjr’s tenure as manager.
However, that never seemed likely from the start, as Atalanta jumped out to an early lead and scored within 15 minutes.
It only took a simple, hopeful pass into United’s half to split the home defense, as Atalanta worked the ball nicely to find Davide Zappacosta, whose low cross was turned into the net from close range by Pasalic. Atalanta’s second goal was even worse, at least from the perspective of Manchester United.
Teun Koopmeiners’ corner, which was headed home by the completely unmarked Demiral, was all it took to break down the United defense this time.
Atalanta’s two first-half goals only served to highlight United’s recent defensive struggles, which have seen Solskjr’s side keep just one clean sheet in their previous 20 matches.
After being found in the box by a wonderful first-time pass from Fernandes, Fred had a great chance to cut the deficit in half, but he could only bend his shot wide of the post. Ronaldo, who had been a mere spectator thus far, held his arms outstretched in frustration, as if expecting a pass.
Rashford was then played clean through on goal moments later, but his shot clipped the top of the crossbar in the final effort of an exciting first half.
The home fans booed as the United players walked off the field, but those boos quickly turned to cheers in the second half.
Rashford finally got his goal, running onto Fernandes’ through ball and slotting the ball brilliantly into the far corner, and United looked like a completely different team. That goal changed the game’s dynamic, and it seemed like it was only a matter of time before United found an equalizer, but goalkeeper David De Gea still had to make two crucial saves to prevent Atalanta from regaining its two-goal lead.
Fortunately for United, it has a player this season who has scored significantly more Champions League goals than that – 136 more to be exact.
Ronaldo’s career has been defined by big goals in big moments, and the Portuguese forward now has another to add to the list, as he headed home from Luke Shaw’s brilliant cross to notch his 137th goal in this competition and send Old Trafford into a frenzy.
Few inside Manchester United’s stadium will have been happier with that goal than Solskjr, who has been forced to brush aside an increasing number of questions about his job security following a string of poor results.
The win will relieve some of the pressure – for a while, at least – but the Norwegian coach knows his team still has a lot of work to do after that first-half performance.
Despite being rock bottom at halftime, United now leads Group F, and its fans will be hoping that second half performance is a sign of things to come.