Juan Mata scored the only goal as Manchester United recorded an underwhelming 1-0 victory over FC Rostov on Thursday to reach the Europa League quarter-finals.
Mata struck 20 minutes from the end of a subdued game, completing a 2-1 aggregate win that sent United into the last eight of Europe's second-tier club competition for the first time since 1985.
But victory came at the cost of an injury to world-record signing Paul Pogba, who left the fray with an apparent hamstring injury early in the second half at an unseasonably cold Old Trafford.
United manager Jose Mourinho said Pogba's injury was due to "fatigue" and hit out at unnamed "enemies" in an apparent reference to his side's jam-packed fixture schedule.
"Normally the enemies should be Rostov, but we have a lot of enemies," Mourinho told BT Sport.
"It's difficult to play Monday with 10 men (against Chelsea). It's difficult to play now. It's difficult to play 12 o'clock on Sunday (against Middlesbrough). We have a lot of enemies."
United, who have never previously won the Europa League, will discover their last-eight opponents in Friday's draw in Nyon.
Mourinho's men are seeking to add the trophy to the League Cup they won last month and have the extra incentive of knowing it will yield a place in next season's Champions League.
Mourinho kept faith with the back three he had deployed in Monday's 1-0 FA Cup defeat at Chelsea, but whereas it was a defensive tactic at Stamford Bridge, there was very little defending to do against Rostov.
Decried for a below-par display at Chelsea, Pogba was able to spray diagonal passes around to his heart's content, such was the Russian side's stubborn determination to defend the edge of their own box.
Marcos Rojo had an early header swatted away by visiting goalkeeper Nikita Medvedev, with Zlatan Ibrahimovic putting the rebound against the post from a tight angle.
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Henrikh Mkhitaryan ran through and chipped wide from Mata's pass and might have won a penalty in the 27th minute following a push by Medvedev, but Lithuanian referee Gediminas Mazeika said no.
Ibrahimovic also saw a shot deflected over by Medvedev and later left the right-hand post quaking with a thunderous shot, while Pogba's left-foot curler drew a full-length save from Medvedev.
Pogba departed in the 47th minute, Marouane Fellaini taking his place, and Rostov briefly threatened to take the upper hand, Sergio Romero saving from Sardar Azmoun and Christian Noboa.
United also lost Daley Blind after he took a bang to the head, which resulted in the curious sight of Phil Jones coming on as a jobbing left wing-back.
The hosts finally made the breakthrough in the 70th minute after Mata intercepted a loose pass in midfield and spread the ball wide to Mkhitaryan on the United right.
The Armenian's low cross was back-heeled towards goal by Ibrahimovic and Mata charged in at the back post to slam home from close range.
Aleksandr Bukharov, Rostov's scorer in the first leg, threatened to peg United back in the 79th minute, but Romero was equal to both his glancing header and Noboa's dangerous stoppage-time free-kick.
A major threat to United in the next round could be Schalke, who grabbed a 2-2 draw at fellow German side Borussia Moenchengladbach to sneak through 3-3 on away goals.
Also narrowly through are in-form Lyon, who went down 2-1 at Roma on the night but held on to progress 5-4 over the two legs.
"Roma are one of the best teams in the tournament so this is an achievement," said Lyon coach Bruno Genesio.
"We were brave and showed a lot of solidarity, virtues which are indispensable against such opposition."
Genk advanced to the quarter-finals as expected after they held Belgian compatriots Gent 1-1 at home, easing through 6-3 on aggregate.
Completing the last-eight line-up are Celta Vigo, Anderlecht, Ajax and Besiktas, who had Cameroon striker and goal-scorer Vincent Aboubakar sent off in the first half but still smashed Olympiakos 4-1 at home.