The left-armer will be sidelined for up to three weeks after pulling up while bowling on the first day and our Director of Cricket Mick Newell admitted he would be missed.
Newell said: "Ryan has been in terrific form for us all season and it?s very disappointing to see him injured.
"He would have had a big role to play in Twenty20. The only consolation is that we have a wider choice of replacements for him in this competition than in the Championship."The 27-year-old is our leading wicket-taker this season, with 30 first-class wickets at an average of 22.