Tottenham star Son Heung-min went off injured less than 20 minutes into Sunday's Premier League clash against Arsenal.
The South Korea international pulled up in the first half after chasing the ball as he appeared to have sustained a hamstring injury.
He was subsequently replaced by Erik Lamela.
What happened after Son was substituted?
Son's replacement went on to score the opening goal in the north London derby clash less than 15 minutes after coming off the bench.
Sergio Reguilon sent a low cross into the box and Lucas Moura was there to tee Lamela up to send a stunning rabona effort into the net.
But Lamela would go from hero to zero after he was sent off late in the second half following two Arsenal goals in response, with Spurs unable to mount a comeback to seal a result.
How important has Son been for Spurs?
Son has been a crucial player for Jose Mourinho's men this season.
The 28-year-old has scored 13 goals and assisted nine in 27 appearances in the Premier League this season. Only Harry Kane, who has netted 16 and registered 13 assists, has contributed to more goals this season.
He has been a mainstay in the starting XI in the Premier League this season, having featured in every game in the English top flight.
Son suffered a minor hamstring injury against Newcastle in September and subsequently missed a Europa League qualifier and Carabao Cup match.
What has Mourinho said on Son's injury?
"That's football," the Portuguese remarked in his post-match press conference. "I don't know how long [a layoff could be].
"It's muscular. Muscular is usually not easy [to recover from]. He's normally a guy who recovers quickly.
"It's [come from] an accumulation of matches. I gave him 30 mins rest in the last match, but it's still 60 [minutes on the field]."
What games could Son miss?
A hamstring injury could see Son ruled out for several weeks.
After Sunday's game, Spurs will turn their attention to their Europa League match against Dinamo Zagreb on Thursday. Mourinho's side won the first leg of the last-16 tie 2-0.
Three days later, they have an away game against Aston Villa and a trip to Newcastle awaits them after the international break.
Tottenham also have a home game against Manchester United coming up on April 10.