Hit: Simon Kjaer (AC Milan)
The former Sevilla centre-back popped up with a late header to secure his side a valuable away goal and keep the contest in the balance ahead of the second-leg.
Kjaer, who has improved Milan's defense considerably since joining last year, is largely underrated by the media and fans alike.
But he reminded everyone of his importance to the side with an excellent defensive performance, capped off with a crucial away goal too.
The Danish international connected with Rade Krunic's corner and powered an unstoppable header beyond Dean Henderson in the 92nd minute.
He'd hadn't scored for Milan this season. The timing of his first goal of the campaign couldn't have been more dramatic.
Flop: Anthony Martial (Manchester United)
What has happened to Martial this season? In unstoppable form last year, scoring goals galore, he's struggled for consistency in the current term.
Tonight he had another poor game and hobbled off at half-time with an apparent injury, piling on further misery.
Martial mustered just one shot on target in the opening stanza, drawing a fine save from Donnarumma, but he was ineffective in possession too.
In fact, the 25-year old was dispossessed twice, even in such a limited time frame, and laid just six passes in 45 minutes.
To make things worse for him, Diallo, who replaced Martial at the break, scored just minutes into the restart and will now have a chance to start the San Siro leg next week ahead of him.
Hit: Franck Kessie (AC Milan)
Sky's the limit for Kessie, who's been a revelation for the Rossoneri this season, and put up another masterclass at Old Trafford.
The strapping Ivorian's physicality allowed him to dominate on the ball and provide excellent protective cover to Milan's back-four.
Going forward too, he was dangerous, and it's a shame that his wonder goal wasn't allowed to stand due to a ridiculous handball ruling.
Without several key players in the lineup, Milan needed a new talisman, and Kessie gave them exactly that.
It's about time we started taking him seriously.