Cologne - Borussia Mönchengladbach have suffered a major setback after Patrick Herrmann was ruled out for at least a month with a knee injury.

Herrmann was diagnosed with an anterior cruciate ligament tear in his left knee after undergoing medical examination for pain in the joint.

The 24-year-old will now undertake an intensive four-week course of rehabilitation before a further assessment, which could determine whether or not the Germany midfielder will require an operation.

Should Herrmann need to undergo surgery, he could be sidelined for up to six months.

The Gladbach youth academy product, who suffered an injury to the same knee in September's friendly against Swiss side FC Sion, had scored one goal and registered an assist in six Bundesliga outings this season.