The Portuguese international Vitor Baia suffered a neck injury in training on Tuesday, while his understudy Carlos Busquets is still recovering from a knock. Bobby Robson, the club's coach, was left with no choice but to call up Lopetegui, compounding the former England manager's problems.
Barcelona were stunned at the weekend by their 4-0 Spanish League defeat at Tenerife, a result that left Robson's side nine points adrift of the leaders Real Madrid.
Apart from Vitor Baia, Robson will also be without the midfielder Oscar Garcia and possibly the Portuguese defender Fernando Couto through injury. Emmanuel Amunike is cup-tied because of previous appearance for his former side, Sporting Lisbon.
However, Robson will be able to call upon the services of his key striker Ronaldo, who missed last week's Spanish Cup game against Atletico Madrid because of international duty with Brazil.
Ronaldo may enjoy himself against AIK, a team regarded as one of the softest options remaining in the competition. The difference between the two sides may become more evident due to the Swedes' lengthy winter lay- off.
Stefan Soderberg, the AIK manager, said yesterday that he was pleased with his team's performance in a Scandinavian club competition held in Cyprus last week. AIK reached the final, which they lost, but beat Norway's Lillestrom in the semi-final.
The Swedish international defender Patrik Englund has not played since a knee ligament operation last October. "We're facing one of the best teams in the world on Thursday, so anything we can do to disrupt them is positive," Soderberg said.
Italy's Fiorentina will be hoping their Argentinian striker Gabriel Batistuta rediscovers his form for tonight's Cup-Winners' Cup quarter-final with Benfica.
With both teams struggling in their domestic leagues, success in Europe offers the chance of salvaging some glory from a disappointing season.
Fiorentina, with the usually prolific Batistuta suddenly finding scoring difficult, are languishing 12th in the Italian League, only five points clear of the relegation zone. Benfica are third in Portugal - but are 14 points adrift of the leaders, Porto.
"It is a challenge that is going to stimulate both sides. We are going to do everything possible to make the next round," Manuel Jose, the Benfica coach, said.
Both teams have injury problems and several key players cannot be used because they have already played for other teams in Europe this season.
The Brazilian midfielder Amaral, formerly of Italy's Parma, and the Dutch winger Glenn Helder, the former Arsenal player, will both be watching from the stands where they could be joined by Benfica's playmaker Valdo, who has injured his right leg.
Fiorentina will be without the former Everton winger Andrei Kanchelskis and the injured midfielder Massimo Orlando, but the Italians will be happy enough if Batistuta, their inspirational captain, can rediscover his touch in the first leg.
The Argentinian has been criticised for some poor performances recently, but his coach, Claudio Ranieri, believes he will prove his worth against Benfica, twice winners in the European Cup but looking for their first Cup-Winners' title.
"Gabriel [Batistuta] is not the sort of player who gets depressed... I think you'll find that he has a great wish to prove to everybody that he is still the same Batistuta," he said.
Paris St-Germain will be looking for a face-saving victory over AEK Athens in their Cup-Winners' Cup quarter-final first leg tonight.
The holders, aiming for a fifth successive European semi- final, sank to a new low on Saturday with elimination from the French Cup by Fourth Division amateurs Clermont.
PSG came through one crisis earlier in the season when they beat Galatasaray 4-0 at home in October to reach the quarter-finals 6-4 on aggregate.Reuse content