Top scorer Neil Harris will be missing as Millwall aim to step up the pressure on the promotion pack with victory at Carlisle United tonight.
Chopper, who was named the Coca-Cola League One Player of the Month for February following a return of five goals in as many games, was forced off with a sore knee after 49 minutes of the 2-2 draw at Walsall on Saturday.
The 32-year-old frontman sits out this evening's Brunton Park clash but could be back in contention for this weekend's derby at home to Charlton Athletic.
Ashley Grimes is the lone addition to the Millwall squad, with Jon Obika or Shaun Batt possibly partnering Steve Morison up front.
Meanwhile Carlisle United will be without striker Darryl Duffy, who sustained a groin injury in Saturday's 0-0 draw at Wycombe Wanderers.
Duffy could be replaced by striker Richard Offiong, who returns to the side after a loan move to Rotherham broke down. Former Lions goalkeeper Lenny Pidgeley is unlikely to start having been replaced by Adam Collin between the sticks in recent games.