Green Bay Packers head coach Mike McCarthy has admitted that the injury to quarterback Aaron Rodgers is a major blow for his side.

Rodgers was forced off during the first drive of the Packers' shock defeat to the Chicago Bears last night, having injured his shoulder while being sacked by Bears defensive end Shea McClellin.

Seneca Wallace struggled to make an impact having come on for Rodgers, throwing for 114 yards with one interception, and McCarthy believes that it is unrealistic to expect a back-up player to match Rodgers's contribution.

"Aaron's a huge part of our offense. This is a thing that's been built over time with Aaron as the centerpiece. I don't think it's realistic to put anyone in there and expect him to perform [like Rodgers]," McCarthy told The AP.

"Seneca, he needs to perform better and he'll definitely do that with a week of practice."

The Packers' defeat means that they are now tied with the Bears and the Detroit Lions at the top of the NFC North.