"Unfortunately, the worst fears have been confirmed: it's a torn cruciate ligament," he wrote on his Facebook page.

"I have the operation on Thursday and straight away THE FIGHT FOR MY COMEBACK BEGINS!"

The 28-year-old suffered the injury just two minutes into Borussia's 2-2 draw at home to Augsburg on Saturday.

He is the the second Dortmund star sidelined with a long-term knee injury this season after centre-back Neven Subotic suffered the same fate in November.

"We have only bad news," said Dortmund coach Jurgen Klopp, whose side have picked up just five points in their last seven league games.

They are 14 points behind leaders and defending champions Bayern Munich.

"For us this is a disaster, but mainly it's terrible for Kuba (Blaszczykowski). Something like this seems to fit into our season so far, but there has to be a cut-off point (to the injuries) eventually."

Klopp had to patch together a team for most of December as at one point he lost his entire back four to injury.

He is still without injured pair centre-back Mats Hummels and midfielder Ilkay Gundogan.