Toulon backs coach Pierre Mignoni will leave the European champions at the end of the season to take over as head coach of Top 14 rivals Lyon.
Lyon – currently last in the Top 14 standings, seven points from safety – have confirmed the arrival of the 38-year-old former French international for the next three seasons.
Alongside manager Bernard Laporte, Mignoni has helped Toulon to two European Cups and one Top 14 title.
Laporte's departure at the season is believed to be one of the main reasons Mignoni has looked elsewhere to further his career.
There will be some stability amongst the Toulon staff, however, with the French giants confirming on Monday that forwards coach Jacques Delmas has signed to stay with the club until June 2017.
"We are delighted Pierre is coming here. He will bring rigour, experience at a very high level, hard work and enthusiasm and a winning mentality which will be major advantages for our club in the coming years," Lyon president Yann Roubert said on the club website
The Toulon, Beziers and Clermont scrum-half won 35 caps for France between 1997 to 2008.
Mignoni is the second Toulon man to make the switch to LOU for next season after the club confirmed the appointment of Sébastien Bruno as forwards coach to replace Olivier Azam, who is joining Oyonnax as sporting director.
"It is with much desire that I have signed up to join the LOU project," said Mignoni.
"The only one thing that keeps me going is to win and have competitors with me. It's with hard work and diligence that we will achieve great things."