The 26-year-old has reportedly been coveted by a handful of Premier League clubs, including Arsenal, Manchester United, Chelsea and Liverpool.
Last summer, Barcelona were thought to be interested in signing the midfielder, but a transfer failed to materialise.
"We are here to help players to improve, that is the case with him," The Mirror quotes Rivere as saying. "Mika Seri is in the same category.
"A very good player who has brought a lot to the club and can legitimately have that desire to go and play abroad."
Seri has been a Nice player since 2015.