Athletic Bilbao manager Ernesto Valverde is facing a mounting injury crisis as his side prepares for a daunting UEFA Europa League semifinal second leg against Manchester United at Old Trafford.

With the Basque outfit trailing 3-0 from the first leg, hopes of a miraculous comeback have taken a hit following uncertainty over the fitness of key players Nico Williams and Oscar de Marcos.

Nico Williams, who has Ghanaian roots and has been one of Bilbao’s standout performers this season, is struggling with a recurring groin injury. The talented winger has been playing through pain in recent weeks, but his condition appears to have worsened.

“He’s making an effort to be there but he’s not well. He finished the other day very badly, and it hasn’t improved,” Valverde said. “He won’t be able to play tomorrow and we’ll have to evaluate him day by day.”

De Marcos is also in doubt after picking up a knock, compounding Valverde’s concerns ahead of the high-stakes encounter. The manager acknowledged the tight fixture schedule has taken a toll on the squad, admitting that managing player fitness through the final stretch of the season is proving to be a challenge.

While midfielder Oihan Sancet is expected to be available, Valverde remains cautious, especially with the season’s climax drawing near.

The potential absence of Nico Williams, whose creativity and pace have been crucial to Bilbao’s attacking play, would be a major blow as they attempt to pull off the near-impossible against the Red Devils.