Worcestershire captain Joe Leach will miss the remainder of this season because of a stress fracture in his back.
It is a significant blow for Worcestershire as Leach is their leading wicket-taker in this year's Specsavers County Championship and Royal London One-Day Cup.
The county are through to the semi-finals in the latter competition and the loss of Leach comes just a week after fellow fast bowler Josh Tongue was ruled out until August with a foot injury.
Head coach Kevin Sharp has not yet decided on a new skipper for Sunday's last four clash against either Nottinghamshire or Kent at New Road.
He said: "It is a big blow and Joe is gutted and quite upset at the minute. He has played such a major part for the club over the last few years.
"It is life. Bowling is a very physical job. Joe has had very few injuries but very rarely do bowlers go through their career without some sort of injury.
"We now have to regroup a bit. We have lost our captain for the rest of the season and we will have a think about things and sort that out over the next week.
"The lads will also be gutted but there is a great spirit in this squad and they will want to do it for Joe on Sunday.
"It means there will be an opening for others that might not have had an opportunity. We want the lads to stand up and be counted - and I'm sure they will."
Leach, who suffered the injury in Worcestershire's final One-Day Cup group game against Warwickshire on June 7, has taken 23 Division One wickets at an average of 22.08 this term.
However, Worcestershire have lost four and drawn one of their opening five matches to sit bottom of the table.