City said the full extent is not yet known, but reports have claimed he could be sidelined for four months.
This knee injury is reportedly similar to the injury he picked up back in 2016 against Everton which ruled him out of action for a similar amount of time that is being reported today.
According to www.metro.co.uk, De Bruyne faces around two months out after suffering the injury when he caught his studs in the turf before leaving the training ground on crutches.
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Boyata told Belgian website DH.be: 'When I hear I've refused to play since I came back from vacation, it's wrong. There have been contrasting reports surrounding the player's fitness following the end of the World Cup .
"We don't just rely on one player".
City became the first team ever to win 14 successive English top-flight games when they triumphed 2-1 at Old Trafford last December.
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However, the United hierarchy were prepared to pay £100m to land Raphael Varane had Real Madrid been willing to sell. United have failed to win the Premier League title since the retirement of Sir Alex Ferguson in 2013.
The Belgium global enjoyed a brilliant campaign last season, scoring eight goals and setting up another 16 as City romped to Premier League success. "Obviously it's a big loss but we've got more than enough cover". And De Bruyne's injury could present an early opportunity for exciting youngster Phil Foden.
"He had so much impact on our game".
KDB was part of the Man City side that impressed last season, narrowly missing out on the PFA Player of the Year award.
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The former Wolfsburg player has been City's talisman since joining the club in August 2015, and was many pundits' choice for Player of the Year during the 2017/18 season as he guided Manchester City to a 100-point total and a Premier League title.