Manchester City striker Sergio Aguero has been playing with a heel injury for much of the season, sources close to the player have told ESPN FC.
Argentina striker Aguero picked up an injury in August and has been receiving regular treatment to manage the situation.
ESPN FC has been told that Aguero has been suffering from swelling on the back of his heel due to the accumulation of excessive fluid.
The 29-year-old has still managed to score 13 times in 19 appearances for City this season and started Saturday's 4-1 victory over Tottenham Hotspur.
He is determined to play his part in the squad and appeared frustrated when he was substituted early in the second half of the win over Spurs.
The striker was taken off in the 56th minute, with the score still 1-0, and threw his gloves to the floor, appearing to ignore Pep Guardiola as he returned to the dugout to be replaced by Gabriel Jesus.
City boss Guardiola said in his postmatch news conference that he understood Aguero's frustration at being substituted because he is a "top player."
Aguero missed over three weeks of the season between September and October after fracturing a rib in a car crash in Amsterdam. However, his heel injury is not related to that incident.