The 32-year-old all-rounder has been troubled by a persistent shoulder problem despite surgery last winter.
He has not played since their T20 Blast game against Derbyshire on 18 July and is only averaging 25.25 in County Championship Division One this season.
“Since the operation he has had a frozen shoulder which we really couldn’t do much about but now he is getting in a lot of good rehab work,” head coach Alan Richardson told the club website., external
“It is now what they call defrosting and it’s an opportunity for him to get some good work done and to put himself into a really good place going into the back end of the season.
“It has been painful throughout the season and he’s done an amazing job to get through as much cricket as he has done.”