The German was partaking in Manchester City's final training session at Estádio do Dragão ahead of Saturday's Champions League final.
As it was open to the media, Marcelo Bechler of TNT Sports first reported Gundogan had limped off the field after a collision with Fernandinho.
In a video which quickly emerged, Gundogan seemed to point towards his thigh when Sergio Agüero asked about his problem and the physios were quick to enter and remove the midfielder from the field.
Further footage of Ilkay Gundogan leaving the field of play after the open training session has emerged on social media taken from a live stream of the session, and appears to indicate the player suffering from a very minor limp.
However, fears of him possibly missing the game were eased when Fred Caldeira tweeted he will be NOT ruled out of the mammoth fixture.
The 30 year-old has been pivotal to all of Manchester City's success so far this season, topping the clubs Premier League goals chart with 13.
It's extremely likely Gundogan was going to start tomorrow's game, so any injury concern could present manager Pep Guardiola with a massive selection headache ahead of one of Manchester City's most important games in their modern history.
A further update from journalist Andy Hampson has revealed Gundogan took a 'bang' to the thigh, but Manchester City do not believe it's anything serious.
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