Tottenham striker Harry Kane suffered a "significant lateral ligament injury" to his left ankle following a collision with Manchester City full-back Fabian Delph, according to a statement from the north London side on Thursday.
"Investigations are ongoing and he will continued to be assessed by our medical staff over the coming week," the statement read.
Dele Alli also fractured his left hand during the Champions League quarterfinal first leg.
It's unclear how long Kane and Alli will be out, but any long-term absence would hamstring a Spurs side chasing a top-four finish and a place in the Champions League semifinals.
Tottenham will host Huddersfield Town on Saturday before facing City in both the Champions League and the Premier League over the space of a week.
Alli will be assessed before the fixture against Huddersfield.
Kane missed more than a month of action with an injury to the same ankle earlier in the season. However, Tottenham managed to win four of seven matches in the 25-year-old's absence.