CHARLOTTE — The Panthers knew they'd be without backup quarterback Sam Darnold for a bit; now they know it will be at least a month.

The Panthers cleared the roster spot to officially sign kicker Eddy Piñeiro Thursday by placing quarterback Sam Darnold on injured reserve.

By carrying Darnold to the 53-man roster before putting him on IR, the Panthers can activate him in as few as four weeks. Since head coach Matt Rhule said Darnold would miss "at least four weeks," that timing works out.

Darnold suffered a high left ankle sprain during the preseason finale last Friday.

In his absence, the Panthers have starter Baker Mayfield and backup PJ Walker on the roster.