Somerset have secured Tim Groenewald on loan until the end of the season, after which they will sign the Derbyshire seamer on a permanent basis.
Groenewald recently advised Derbyshire of his intention to leave the county when his contract expires at the end of the current campaign, declining an extended deal.
The 30-year-old former Warwickshire man played 72 first-class matches for Derbyshire, taking 229 wickets at an average of 29.
Groenewald also helped himself to 103 scalps in the limited-overs formats and won his county cap in 2011.
Derbyshire elite performance director Graeme Welch said: "Tim has been a terrific player for Derbyshire and we respect his decision to move on. We wish him and his family all the best for the future.
“We started discussions about a loan move immediately after Tim advised us that he would not be accepting our offer of a contract extension.
“We will continue to work hard on turning around our fortunes on the pitch this season, as we build towards our long-term ambition of success in all formats of the game.
“We have an exciting crop of young seam bowlers coming through, who have a great opportunity to show us what they can do and to gain valuable first-team experience.
“Tim’s departure also frees up some playing budget as we continue looking to strengthen the squad with seasoned pros who can win cricket matches, as well as leading and nurturing the club’s emerging young talent.
“If we need to bring someone in on loan during the interim – that is something we could also look to do.”
Derbyshire captain Wayne Madsen added: “I'd like to thank Tim for everything he's done for the club. He's been a great team-mate and friend.”