Chelsea suffered a big setback as Christopher Nkunku hobbled off hurt during a preseason friendly.

The Blues were on a tour of the United States when new signing Nkunku landed awkwardly on his knee against German heavyweights Borussia Dortmund.

Mauricio Pochettino and his coaching staff held their breath as the big-money recruit was treated on the field.

Unfortunately for Chelsea fans, he was unable to continue and was eventually replaced.

Depending on the severity of the injury, it may be a major setback for Chelsea’s recovery as they seek to avenge last season’s humiliation.

However, while the severity of the event is still unknown, Blues fans are pointing their fingers at the surface.

Soldier Field in Chicago does not appear to have a particularly comfortable playing surface, with the ball bobbling around all over the place.

Fans have taken to social media to express their outrage, with many labelling the pitch ‘disgraceful’ and directly blaming it for Nkunku’s injury.