Leeds' automatic promotion hopes have been dealt a blow after boss Marcelo Bielsa revealed Kalvin Phillips could miss the rest of the season.
Key midfielder Phillips, who played the full 90 minutes in Sunday's 1-0 win at Swansea, has definitely been ruled out of this week's home game against Barnsley due to a knee injury.
"Kalvin is not going to play in Thursday's match," Bielsa said. "We don't know if he's going to play the next two matches as well.
"He has a problem in the knee and probably is not going to be involved in the last three, but in the worst scenario it's an injury we are going to resolve in four or five weeks."
Phillips has made a significant contribution to Leeds' promotion push this season, with his displays in the midfield holding role earning praise from England manager Gareth Southgate.
The 24-year-old emerged for the second half at the Liberty Stadium wearing heavy strapping on his knee.
Bielsa suggested on-loan central defender Ben White could play in Phillips' role against Barnsley, meaning a possible recall at centre-back for Gaetano Berardi.
Pablo Hernandez's late winner at Swansea left Leeds needing four more points from their last three games to seal a return to the Premier League for the first time since 2004.
Leeds will be guaranteed a top-two finish if promotion rivals Brentford fail to beat Preston at Griffin Park on Wednesday and Bielsa's side take three points from the visit of relegation battlers Barnsley.
Bielsa is satisfied his players have retained their focus after the joyous celebrations on Sunday which followed Hernandez's late winner.
"The happiness after winning with a last-minute goal is very visible for everybody," Bielsa said. "When the hours progress it all returns to normal.
"Professionalism allows you to choose the best moves for the competition.
"They know how to manage the emotions that make them stronger and weaker as well. It's necessary to manage those emotions to compete in the right way."
Bielsa reported no other major new injury concerns and said he had yet to decide whether Kiko Casilla will return in goal.
Spaniard Casilla has served an eight-match ban after being found guilty of racially abusing Charlton's Jonathan Leko in February.
Casilla, who denied the charge, was also fined £60,000, while French goalkeeper Illan Meslier has conceded just two goals in his absence.
