Ignacio Mieres will leave Exeter Chiefs at the end of the current campaign to join Aviva Premiership rivals Worcester.
The Argentina fly-half has made 51 appearances for the Chiefs since his arrival in October 2010 and has scored 395 points.
However, he has fallen behind Gareth Steenson in the pecking order at the Devon club and has decided to move on to improve his chances of international selection.
Exeter head coach Rob Baxter told the club's official website: "Nacho is wanting to play more rugby, get more starts, and right now he is feeling that will happen more often at another club.
"What we have at the moment is a guy who is very passionate about playing - and he is desperate to play more for Argentina.
"I think because of those factors, he feels he now wants to go somewhere where he is going to start regularly and put himself in the shop window to get the best opportunity to play international rugby.
"It is a shame, of course, because we never like signing anyone here and them not seeing out their contracts.
"We're not going to be awkward and stand in his way, especially with the fact he feels he would like to go somewhere else.
"Obviously there were opportunities for him to play in the future, but I guess it's one of those things."