Captain Dean Mumm has admitted he will be sad to end his Exeter Chiefs career at the end of the season.
The Australia international has confirmed he is to re-join former club NSW Waratahs and hopes to earn a place in his country's squad for the World Cup in England later this year.
The forward, 31, said: "I'm only leaving to chase an opportunity that I didn't think was otherwise present.
"It will be sad to leave, but in the meantime there is so much to focus on."
Mumm joined Exeter in 2012 and led them to LV= Cup success last season - the Devon club's first major trophy.
"In my time here, the club has grown enormously," he told the club website.
"Not just in terms of the stands and the seating capacity, but in terms of what we are now looking at and where our ambitions lie.
"I think evidence of that is shown in some of the recent signings that we've made. There are players who have played in the UK for a long time, who are very experienced, very talented, and who now see Exeter as not only an option to play some excellent rugby, but where they can ultimately enjoy their rugby as well."
Mumm also praised the "family" environment that has been created at Sandy Park, adding: "When I first arrived here there wasn't a huge amount of people from Exeter, and by that I mean there were people from different parts of England, as well as from other parts of the world.
"And that in itself meant we created almost a family of our own, who were there for one another not just on the pitch, but off it as well. Here I've been able to create friendships that will be with me for life and I'll never forget that."