St Etienne 0 Manchester United 1 (Man United win 4-0 on aggregate)
Manchester United secured Europa League progress at a cost, with Henrikh Mkhitaryan limping off shortly after opening the scoring against St Etienne to put his EFL Cup final hopes in jeopardy.
Jose Mourinho named a surprisingly-strong line-up considering they arrived in France boasting a 3-0 lead for the last-32 return leg - a bold decision that backfired somewhat.
In-form Mkhitaryan limped off after 25 minutes in St Etienne holding the back of his right leg, having already set United on course for a 1-0 second-leg win by directing home a fine Juan Mata cross.
The 16th-minute strike was the fifth goal the Armenian had been involved in during his last six matches, underlining just how large a blow his absence against Southampton at Wembley this Sunday might be.
Michael Carrick may also have sustained a calf complaint before departing in the second half, moments before Eric Bailly saw red after picking up two yellow cards in 185 seconds.
United responded manfully to the sending off and held firm to keep a fourth successive clean sheet in European competition and secure their place in Friday's Europa League last-16 draw.
Pre-match odds as long as 40-1 on St Etienne going through highlighted what an uphill task the hosts faced, yet their fans turned out in their droves at the Stade Geoffroy-Guichard.
A remarkable din greeted the team for the warm-up, never mind the match itself, although UEFA will again take a dim view to the use of flares that led to disciplinary action after the first leg at Old Trafford.
Les Verts' intensity and endeavour had proved problematic last week, but this time Mourinho's men did not attack with the same numbers that saw them caught out last time.
But when United first threatened, they left St Etienne with a bloody nose and all-but settled the tie.
Mata sent in a superb, low cross from the left flank and Mkhitaryan provided a deft touch, having burst in-between the home side's centre-backs to the edge of the six-yard box.
St Etienne goalkeeper Stephane Ruffier prevented matters quickly being compounded by an own goal, although United's comfort was tempered by Mkhitaryan pulling up injured.
The 28-year-old's game was over inside 25 minutes yet the setback did not disrupt United too much as Ashley Young threatened and Zlatan Ibrahimovic fired over before half-time.
Loic Perrin's header at Sergio Romero's goal was the closest St Etienne came in the first half and the hosts failed to create any clear-cut chances despite returning from the break brightly.
Marouane Fellaini smashed into the side-netting and Ruffier got down to stop a Paul Pogba strike as United threatened a second, before Carrick went off with what looked like a calf problem.
That change was squeezed in-between Bailly bookings in the 60th and 63rd minute for fouls on Romain Hamouma, leaving Mourinho understandably frustrated.
Florentin Pogba fired wide before younger brother Paul glanced a corner just off target at the other end.
Substitute Marcus Rashford and Ibrahimovic, jeered all night by the home fans, failed with late efforts, while Jorginho stung the palms of Romero in stoppage time as the home fans continued to roar on their team.