Guthrie, who apologised after refusing to participate in the 3-0 defeat at Sunderland earlier this month, impressed manager Brian McDermott on his comeback to the side in the Royals' Boxing Day draw with Swansea.
Veteran striker Jason Roberts has missed the last four matches with a hip injury. Defender Sean Morrison is still sidelined with ankle injury and goalkeeper Alex McCarthy is out long term with a shoulder problem.
