Wales and Ospreys scrum-half Rhys Webb has confirmed he will move to France at the end of the season.
Sky sources understand Webb, who played in two British and Irish Lions Tests against New Zealand, has agreed a contract with three-time European champions Toulon.
The 28-year-old said: "It's a huge wrench to be leaving the Ospreys after spending all of my playing career with the team.
"I have made lifelong friends on and off the pitch and I cannot speak highly enough of the quality of the coaching team, players and all of the staff involved within the Ospreys organisation.
"I will continue to give the region everything I can to make sure we have the best season possible and I would like to conclude by saying a heartfelt thanks to everyone within the region for helping me achieve my goals within rugby.
"I would like to thank the WRU and the Ospreys for their efforts during this process."
The WRU and Ospreys say they made "every effort" to retain Webb's services but it is a further blow after Dan Biggar announced he was joining Northampton last month.
Webb and Biggar's Wales prospects will hinge on them securing one of four wildcards available to head coach Warren Gatland next season - under the WRU's senior selection policy for players based outside Wales.
That figure drops to just two wildcards in 2019-20, which is also a World Cup season.
The WRU told Sky Sports News they are constantly reviewing this selection policy - and have not ruled out changing it.