Scharner, who spent four-and-a-half years at the DW Stadium before leaving in 2010, has been recruited by manager Roberto Martinez from Hamburg until the end of the season.
The Austrian is set to play in central defence, where Ivan Ramis (knee) and Antolin Alcaraz (groin) are currently unavailable.
Adrian Lopez (hamstring), along with goalkeeper Mike Pollitt (thigh) and midfielders Ben Watson (broken leg), Albert Crusat (knee), Ryo Miyaichi (ankle) and Fraser Fyvie (soft tissue problem) are all still missing.
Forward Arouna Kone is away on African Nations Cup duty and full-back Emmerson Boyce (hamstring) is a doubt.
Pedro stepped off the bench to send Chelsea into the FA Cup semi-finals after they beat Leicester 2-1 at the King Power Stadium on Sunday evening.
RB Leipzig came from behind at the Red Bull Arena to end a run of four winless games and defeat Bundesliga leaders Bayern Munich 2-1 on Sunday.