Erik ten Hag has said he doesn't know how long he will be without Marcus Rashford after Manchester United confirmed the forward would be unavailable for a few games.
Rashford, who has scored 28 goals this season, will miss Thursday's Europa League quarterfinal first leg against Sevilla after suffering a groin injury during the 2-0 win over Everton on Saturday.
- Stream on ESPN+: LaLiga, Bundesliga, more (U.S.)
The club said in a statement on Wednesday morning that Rashford would return "for the season run-in" and speaking at a news conference later in the day, Ten Hag said he could not be more specific about when the 25-year-old might be back.
"A few games so that is the statement," said Ten Hag, who added that Luke Shaw will also be absent against Sevilla.
"I can't give more details because we don't know we have to see how the injury develops."
United are entering a crucial stage of the campaign with four games in 11 days beginning with Sevilla's visit to Old Trafford.
Ten Hag's team face Nottingham Forest on Sunday and then the return leg with Sevilla in Spain before an FA Cup semifinal with Brighton at Wembley on April 23.
A statement issued by United on Wednesday morning read: "Marcus Rashford will be unavailable for Thursday's UEFA Europa League quarterfinal game against Sevilla because of a muscle injury.
"The forward was withdrawn in the 80th minute of Saturday's 2-0 Premier League win over Everton at Old Trafford and immediately headed to the dressing room for treatment.
"Subsequent assessment of the injury suggested that Marcus will be unavailable for a few games, but is expected to be back for the season run-in."
With Rashford sidelined, Ten Hag could have Anthony Martial his first start since Jan. 14. Martial has missed 32 of 49 matches because of injury this season but has come on as a substitute in the last three.
"I think he is ready to start a game but the front line against Brentford did really well and we decided to continue with that against Everton and they did again really well," said Ten Hag.
"The advantage is we can bring Anthony Martial slow back, give him minutes, get him used to high intensity, but against Everton he was ready to start again.
"The stats tell you the moment he is on the pitch the time he needs for a goal is really less and when he is in the team -- I refer to games against Manchester City and Liverpool -- we play our best football and have our best results as a team."
Speaking later on Wednesday, Sevilla coach Jose Luis Mendilibar played down Rashford's absence, saying "We know whoever replaces Marcus Rashford will do well."
But veteran midfielder Ivan Rakitic warned United not to underestimate a club that have won the Europa League four times in the last nine seasons.
"We've had ups and downs in LaLiga this season but we have to think about the here and now," he said. "We've done well in our last two games and we want to continue in this path tomorrow.
"We want to make life difficult for Manchester United. We know it's going to be tough because Manchester United are among the favourites to win but everyone knows the history that Sevilla has in this competition. We want to compete tomorrow, it is our competition and in terms of will and effort, nobody can beat us."
Information from ESPN's Adriana Garcia was used in this report.