Kennedy was taken off as a precaution in the second half of the 1-0 loss at Blackpool on Tuesday.
Stevenage remain in the thick of the promotion battle despite that defeat, lying sixth in the Sky Bet League Two table and 24 points better off than they were at the same stage last season.
Sarll could be ready to refresh his starting line-up as his side take on a Portsmouth team currently third in the table.
Pompey boss Paul Cook will make a late decision on Kal Naismith and Kyle Bennett.
Bennett injured his ankle during their 4-0 win over Grimsby and was forced to hobble off at half-time while Naismith sustained a hamstring injury in the same game. Both men will be assessed prior to the match.
Stanley Aborah and Nicke Kabamba could make their first starts for the club while Amine Linganzi, Gary Roberts and Conor Chaplin are pushing for starting places.
Curtis Main (knee) is a long-term absentee having not featured since October.