United got off to the worst start imaginable as goals from Mario Pasalic and Merih Demiral gave the visiting Italian side a 2-0 lead inside the opening half an hour.
However, United emerged from the half-time break looking like a completely different side and Marcus Rashford’s early strike halved the deficit and got the home supporters rocking.
Captain Harry Maguire then drew United level with a smart finish 15 minutes from time, before a trademark Ronaldo leap and header with just eight minutes remaining secured a 3-2 win to cap another memorable Champions League night under the lights at Old Trafford.
It was imperative United set the tone early on to try and earn the crowd’s affection on a night that would be fraught with tension and perhaps crucial to Ole Gunnar Solskjær’s tenure as manager.
However, from the first whistle that never looked likely as Atalanta began on the front foot and opened the scoring inside 15 minutes.
It took just a simple, hopeful pass into United’s half to pull the home defense apart as Atalanta then worked the ball nicely to find Davide Zappacosta, whose low cross was turned into the net by Pasalic from close range.
Atalanta’s second goal was even worse, at least from a United perspective.
All it took to break down the United’s defense this time was Teun Koopmeiners’ corner, which was headed home by the completely unmarked Demiral.
Atalanta’s two first-half goals only served to highlight United’s recent defensive woes, which have seen Solskjær’s side keep just one clean sheet in its previous 20 matches.
Fred then missed a huge chance to halve the deficit just before the half-time break after being found in the box by a wonderful first-time pass from Fernandes, but the midfielder could only bend his shot wide of the post. Ronaldo, a mere passenger in the game so far, held his arms outstretched in frustration as though he had expected a pass.
Rashford was then played clean through on goal moments later, but his shot clipped the top of the crossbar in what was the last effort of an action-packed first half.
There were boos from the home supporters as the United players made their way off the pitch, but those jeers soon turned to cheers in the second half.
United looked like a completely different team and Rashford finally got his goal, running onto Fernandes’ through ball and slotting the ball brilliantly into the far corner.
That strike changed the entire dynamic of the match and it felt like just a matter of time before United would find an equalizer, but goalkeeper David De Gea still had to make two vital saves to ensure Atalanta didn’t restore its two-goal lead.
Fortunately for United, this season it has a player who has scored considerably more Champions League goals than that — 136 more to be precise.
Much of 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 wild.
Few inside United’s stadium will have been more delighted with that goal than Solskjær, who has been forced to bat away an increasing number of questions about his job security following a string of bad results.
The win will ease the pressure — for a short time at least — but the Norwegian coach knows his side still has plenty to work on after that first-half performance.
United now tops Group F, despite going in at half time rock bottom, and its fans will be hoping that second half display is a sign of things to come.