Tottenham Hotspur's Champions League title hopes took a hit when Harry Kane exited their quarterfinal match against Manchester City with a right ankle injury.
Kane's injury comes at an inopportune time as Spurs also remain in the hunt for securing a top-four spot in the Premier League.
"It's very, very sad. It's going to be tough and we're going to miss him -- maybe for the rest of the season," Spurs manager Mauricio Pochettino told BT Sport at the end of Monday's match.
Pochettino said it was the same ankle that caused Kane to miss six weeks after suffering ligament damage in a Jan. 15 Premier League match against Manchester United.
"It is a worry for us. We hope it is not a big issue. But there is not too much time to recover. He twisted his ankle so we will see how it reacts," Pochettino said.
The injury occurred when City defender Fabian Delph stepped on Kane's foot on a challenge in the 58th minute. Kane's ankle twisted as he slid to the ground, and he later limped off the pitch toward the tunnel with the assistance of team trainers.
Pochettino exchanged angry words with Delph after the incident, in which the City player appeared to stand on Kane's ankle as the pair tussled for the ball.
"He was so aggressive with Harry after the action," Pochettino said. "I tried to explain to him that it wasn't the intention of Harry or him to damage each other, it was a tough action, and Harry twisted his ankle.
"I said to Delph, 'You were lucky,' because they were checking the VAR and technically it could have been a red card. But I think both were fighting for the ball."
Kane, who was photographed leaving the stadium on crutches, has scored 24 goals in 38 appearances in all competitions for Tottenham this season.
The second leg against City is on April 17 at Etihad Stadium. Spurs are back in Premier League action on Saturday against already-relegated Huddersfield Town.
Information from Reuters was used in this report.