Grounds has gone back to Middlesbrough after his loan spell ended so Gunn will be forced into a reshuffle, with Ryan Bertrand expected to move back to left-back from midfield.
Adam Drury (knee) remains out but could return for Saturday's clash with Plymouth while David Carney or Alan Gow could come into the side to provide some attacking threat.
Mark Fotheringham is fit but has been left out of the 16 for the last two games after Gunn admitted he was "disappointed" with his reaction when he was substituted in the closing stages of the 2-1 home defeat by Coventry. Gary Doherty has been named as captain for the rest of the season.
Veteran defender Dejan Stefanovic is in light training following cruciate ligament damage but will not return before the end of the season.
Saturday's 2-0 defeat at Blackpool has left the Canaries three points adrift of safety with just nine games remaining.
Dave Jones is sweating over the fitness of five players ahead the long trip.
Despite scoring on his return from injury during Saturday's 3-0 victory over Doncaster, striker Jay Bothroyd had to leave the pitch after just 36 minutes with a calf problem.
Full-back Mark Kennedy had already made way 10 minutes earlier due to a hamstring injury and both are major doubts for the encounter.
Eddie Johnson, who scored his first goal for the club at the weekend having come on in place of Bothroyd, and Miguel Comminges are standing by to replace the pair, although Ross McCormack will also be competing for the forward berth.
Midfielders Stephen McPhail (stomach) and Chris Burke (calf) and defender Kevin McNaughton (hamstring) are also doubtful having struggled to shake off their respective problems of late.
Michael Chopra, Paul Parry and Gavin Rae all overcame injury to face Rovers at the weekend and are again expected to feature but goalkeepers Tom Heaton (thigh) and Peter Enckelman (knee) remain sidelined.
Sporting Life.