Mitchell Santner’s move to Derbyshire has been cancelled because of a knee injury that has ruled out the all-rounder for six to nine months.
The New Zealand international, 26, signed as the club’s overseas player for the second half of the 2018 season, but he needs surgery on a bone defect.
Cricket advisor Kim Barnett said it was “desperately disappointing”.
“It’s really sad. We’ll miss having him but he must put his long-term future first,” Barnett told BBC Radio Derby.
Santner was due to play in all of the T20 competition and the final seven County Championship games.
He helped New Zealand reach the 2016 World T20 semi-finals and has played the short format for the last two summers with Worcestershire.
Barnett added: “We are already reviewing our options for potential overseas replacements.”