Nayacalevu famously led Fiji to victory over Wales at Principality Stadium earlier this season and was in charge of the team that beat England at Twickenham ahead of the 2023 World Cup.
Watkin was injured during the opening Guinness Six Nations match against France in Paris and will miss the remained of the current campaign. Nayacalevu joims from Sale Sharks, who he joined at the start of the season after playing for the past 13 years in the Top 14 with Stade Francais Paris and Toulon.
The 34-year-old will add experience to the Ospreys midfield as they prepare for a Round of 16 game in the EPCR Challenge Cup against Scarlets on Sunday 6 April and seek another BKT United Rugby Championship pay-off place.
“It’s a real honour to be signing with the Ospreys. There’s some world class talent here and I’m looking forward to playing alongside them,” said Nayacalevu, who has scored 18 tries in 43 tests.
“Stepping into a team where quality experience is combined with exciting potential is ideal for me at this stage of my career. I believe I can contribute heavily to the squad this season, both on the field and off it.
“Having spoken to Mark Jones and watched the Ospreys in recent weeks, I feel the team’s style of play can offer me the perfect platform to deliver my best rugby and this played an important role in my decision.”
Nayacalevu won the EPCR Challenge Cup with Stade Francias in 2017 when they beat Gloucester 25-17 in the final at Murrayfield. On that occasion he played on the wing, while two years earlier he helped the Parisians to win the Top 14 title against Clermont Auvergne.
“It’s not often a player of Waisea’s calibre becomes available in-season. He brings a wealth of experience and leadership credentials with him, which can only be a good thing for our youngsters coming through,” said Ospreys head coach Jones.
“We feel Waisea can make an instant impact and be a real difference maker for us in Owen’s absence, and stands us in good stead in a season where we still have a lot to play for.”
