Harry Maguire (second from left) of Manchester United argues with the referee in the match against Sevilla on Sunday in Cologne, Germany. Photo: IC
Ole Gunnar Solskjaer admitted Manchester United face a busy few weeks in the transfer market after losing a third semifinal this season as Sevilla reached the Europa League final by coming from behind to win 2-1 in Cologne, Germany.
United were made to pay for their profligacy in front of goal after Bruno Fernandes' early penalty put them in front.
Suso quickly levelled for Sevilla before goalkeeper Bono kept them in the game and substitute Luuk de Jong continued the Spanish side's remarkable Europa League run in recent years by slotting home the winner 12 minutes from time.
United had already secured their place in the Champions League next season by finishing third in the Premier League, but an over-reliance on a small core of players was again exposed as Solskjaer did not make a single substitution until three minutes from time.
United's new Premier League campaign could now begin in just over four weeks' time and initial talks over the signing of Jadon Sancho have stalled with Borussia Dortmund insisting the England international will remain in Germany next season.
"We need to strengthen the squad depth of course. It will be a long season," said Solskjaer. "I cannot say when or if transfers are going to be done, but we are looking at it. It is a quick turnaround. We just have to be 100 percent sure when we do those deals."
Sevilla have now won 25 of their last 26 Europa League knockout ties and will believe they are destined to win the competition for a sixth time when they face Inter Milan or Shakhtar Donetsk in Friday's final.
"This is the best Manchester United of the last few years and the form team in England so it is normal that we had to suffer," said Sevilla boss Julen Lopetegui.
"We are very excited for the final, but it will be the hardest game yet and we have to prepare."
Lopetegui is enjoying a renaissance in Seville after a tough couple of years when he was sacked as Spain coach on the eve of the 2018 World Cup for accepting the role as Real Madrid manager and then fired again just months into his time at the Santiago Bernabeu.
Sevilla are now unbeaten in a club record 20 games, but were unsettled by the pace and movement of United's front four early as Marcus Rashford was wiped out by Diego Carlos after his initial effort was saved by Bono.
Fernandes has ensured United's early-season woes from the spot are long forgotten as the Portuguese converted his eighth penalty for the club and the 22nd the Red Devils have been awarded in a 13-month-long campaign.
Sevilla grew back into the game and levelled with a fine team goal on 19 minutes.
On-loan Real Madrid left-back Sergio Reguilon is in demand from a host of top European clubs and his run opened up the United defense before his cross was swept home by former Liverpool winger Suso.
Despite the lack of a crowd in Cologne, there was no lack of passion or tension as Sevilla were roared on by their substitutes, staff and directors and tempers flared with both benches exchanging words.
"It is one of the curiosities of this situation [playing behind closed doors]," added Lopetegui. "The support of your teammates is important."
United rode out the Sevilla storm and had a host of chances early in the second half to go back in front but a combination of Bono, poor finishing and brave last-ditch defending kept them at bay.
Anthony Martial was the biggest culprit as three times the Sevilla's second-choice stopper denied the Frenchman one-on-one as United began to cut through Sevilla at will.
Lopetegui responded by sacrificing top scorer Lucas Ocampos for De Jong and his changes worked to perfection as Sevilla regained their composure before landing the sucker punch.
De Jong has had a difficult first season in Spain, but went a long way to redeeming himself as he was alive to turn home former Manchester City winger Jesus Navas' cross with the United defense sleeping, which led to a confrontation between Fernandes and his teammate Victor Lindelof.