Chelsea manager Mauricio Pochettino has confirmed that Christopher Nkunku suffered a knee injury in their final pre-season friendly.

The Blues were held to a 1-1 draw by Borussia Dortmund on Wednesday.

Nkunku, who arrived from RB Leipzig in a £52 million deal this summer, impressed with three goals during the club’s USA Tour but came off after just 20 minutes at Soldier Field.

The 25-year-old will now be assessed further by the Chelsea medical staff.

“The doctors are checking him, and I hope it is not a big issue. He fell in the action, which was maybe a penalty, and he feels something in his knee, but we hope it is nothing big.

“We took some risks because the pitch is not perfect because the facilities are used for a different sport. We won’t blame the pitch for the injury, though. For me, it was bad luck,” Pochettino said.

Pochettino will be hoping to have Nkunku fit for their Premier League opener against Liverpool next weekend.