Jose Mourinho openly questioned the conclusions of his medical staff after midfielder Ander Herrera was forced off with a "bad injury" despite apparently being deemed "100 per cent ready".
Herrera had missed several weeks of action ahead of Wednesday's 0-0 draw at Sevilla with a muscular problem, before being thrown straight into the action at the Ramon Sanchez Pizjuan.
The Spain international lasted just 17 minutes before appearing to suffer a recurrence of the issue and Mourinho was quick to point the finger at his medical team for saying Herrera was match fit.
"I think it is a bad injury," said the United boss.
"He had a small injury that stopped him for the last couple of matches, but the medical team said he was 100 per cent ready for the last Saturday. We didn't play him to give him more work and protection, but it looks like he wasn't fully fit.
"The medical department gave him fully fit on Saturday. He trained Saturday, Sunday, Monday and Tuesday and he looked fit.
"The way he was playing during the time on the pitch he showed that intensity that is only possible when fit, when you feel fit.
"He was pressing a lot, pressing really high. We started game by not giving one inch to [Ever] Banega, pressing really high and Ander was one of them, Scott [McTominay] the other, and you only do that when you feel good.
"Then there was the back-heel and that causes a contraction in the muscular area where he had the previous problem and now we have to prove that he was not 100 per cent fit."
Sevilla coach Vincenzo Montella was upbeat at full-time, praising the character and performance of his side, though he was left ruing their wasteful finishing.
"We had 10 shots on target and 10 corners in the first half," he said. "We were superior on the pitch, but football is like this.
"Not conceding at this stage is crucial. Now we need to score at Old Trafford and I am confident we will.
"I am proud because the team has shown both quality and character. We had to win, and because of this, we are disappointed for the fans that have been incredible tonight.
"It has been a great night that could have been even better, but it's all to play for now."
|Suns owner Sarver committed to keeping team in Phoenix|
|Chargers WR Allen leaves with injury after near-spectacular catch|
|Socceroos not giving up on Mooy for Asian Cup|
|Cooper says Raiders owner wanted to trade him to Cowboys|
|Pochettino jokes Levy is ´worried´ about losing him|
|Barcelona would welcome Morata – Alba|
|Toure not a priority for West Ham – Pellegrini|
|Koscielny no certainty to face Southampton, says Emery|
|We gifted the game – AC Milan boss Gattuso furious after Europa League exit|
|My season starts now, says Koscielny|
|Cipriani ´at peace´ with latest England snub|
|Laporte: Deschamps must have personal reasons for France snub|
|Morata injury not too serious, claims Chelsea boss Sarri|
|Hansen to leave: All Blacks coach returning focus to World Cup defence|
|I want to fight the champion! - Joshua reiterates Wilder in April ambition|
|Gundogan glad to leave Christmas holidays behind|
|I know how it feels and it hurts - Gundogan on Sterling abuse|
|Celtic 1 Red Bull Salzburg 2: Scottish champions through despite defeat|
|Olympiacos 3 AC Milan 1: Rossoneri crash out of Europa League|
|Arsenal 1 Qarabag 0: Lacazette on target as Saka shines|
|Hansen to leave: All Blacks will take time to name replacement|
|Chelsea condemn alleged anti-Semitic chanting from fans|
|Hansen to leave: The best Opta facts from New Zealand coach´s tenure|
|Hansen to leave: Five contenders to be the next All Blacks coach|
|Hansen to leave: Highs and highs of his All Blacks reign|
|Hansen to leave All Blacks after World Cup|
|Rapid Vienna 1 Rangers 0: Late Ljubicic winner sends Gerrard´s men out|
|Beckham continues to miss Giants practice with quad injury|
|Vidi 2 Chelsea 2: Giroud spares Sarri´s side in lacklustre draw|
|Paris Saint-Germain and Marseille fixtures among latest Ligue 1 cancellations|
|Santos turn to ex-Argentina boss Sampaoli|
|Muller could miss Champions League last 16 after Tagliafico kick|
|Home hope Bekker out in front at Alfred Dunhill Championship|
|Van Bommel in touch with Robben over PSV reunion|
|Pinarello chief confident over Team Sky future|
|Stade make Ospreys tickets free in tribute to teenager|
|WRC great Loeb seals Hyundai switch|
|Madrid rumours better than sack talk, says Pochettino|
|Nadal to join Federer at 2019 Laver Cup|
|Prigoda smashes world record, Hosszu dethroned in Hangzhou|
|Former Juve CEO Marotta takes over at Inter|
|Glenn to stand down as FA boss next year|
|Muller apologises to Tagliafico for kick to the head|
|Pereira pleads for more Manchester United chances|
|Griffin hails ´phenomenal´ Lowry after Warriors demolition|
|I´ve played with Zidane and Henry, but Messi is something else – Pires|
|Dragons forward Jack de Belin charged with sexual assault|
|Durant: Raptors are the real deal|
|Cocu bids farewell to Fenerbahce after ´mutual agreement´ is made over October sacking|
|Australia unchanged for historic Perth Test|
|Champions League draw: The possible last-16 ties|
|Southee happy to be back on home soil|
|I wouldn´t swap Dembele for Neymar – Pires|
|Canelo ready to risk heavy weather against Fielding|
|Raptors upstage Warriors, Davis leads Pelicans with 44 points|
|India skipper Kohli excited by green Perth wicket|
|PSG? I haven´t decided my future yet – De Jong|
|Marcelo: Real Madrid don´t have attitude problem|
|India pair Ashwin, Rohit ruled out of second Test|
|Kovac: Ajax-Bayern draw was amazing|
|Sims re-signs with Dragons until 2022|
|Derrius Guice injury update: Redskins RB (knee) has rehab setback, undergoes 3 more procedures|
|Emery: Arsenal could sign defender in January|
|Phillies sign McCutchen to three-year deal|
|O´Neal thinks his Lakers teams could ´easily´ beat Warriors|
|A-League to add two clubs by 2020|
|Curry says he was ´obviously joking´ about moon landing comments|
|Now the beautiful part starts – Ronaldo ready for Champions League knockout stage|
|Bayern have a lot more potential – Lewandowski not satisfied despite top spot|
|Lyon star Fekir shares plaudits for Champions League progression|