Steven Bergwijn's ankle injury means he is unlikely to play again this season, Tottenham boss Jose Mourinho says.
The 22-year-old Netherlands winger, who joined Spurs from PSV Eindhoven in January for £27m, was injured in Saturday's 1-1 draw at Burnley.
Spurs confirmed on Monday he had suffered a "significant sprain" to his left ankle and faced an "extended period of rehabilitation".
Harry Kane and Son Heung-min are already out with long-term injuries.
In addition, midfielder Moussa Sissoko has been sidelined since 1 January.
Kane, Tottenham's leading scorer for the past five seasons, encouraged Spurs followers on Monday with a message on social media.
The England international, 26, is recovering from surgery to repair a ruptured left hamstring tendon, suffered during the defeat at Southampton on 1 January.
But he posted: "Love being back on the grass with a ball at my feet."
'This isn't a time to get our violins out'
Son could miss the remainder of the season after breaking his arm against Aston Villa on 16 February.
Sissoko, meanwhile, is recovering from surgery on the medial collateral ligament in his right knee.
On Tuesday, Spurs visit German side RB Leipzig in their Champions League last-16 tie, trailing 1-0 from the first leg in north London.
Mourinho's side are without a win in their past five matches but the manager - who revealed defender Ben Davies would return from injury in "one or two weeks" - said of the trip to Germany: "I'm very motivated, I'm very calm and very positive.
"We have to be all together. I believe in the boys and I think we can make it."
Midfielder Dele Alli added that there could be no excuses about the run of bad results and injuries.
"We're in a position where everybody needs to step up and help turn this around," he said.
"This isn't a time to get our violins out. We need to step up and deal with these situations."