Sonny Bill Williams may form a midfield partnership with his rugby mentor Tana Umaga as the former All Blacks captain laces up the boots again.

Under pressure to save his job as manager of struggling French top division team Toulon, 35-year-old Umaga has agreed to end two-years in retirement and return to the field in a bid to stave off relegation.

Toulon president Mourad Boudjellal revealed Umaga's twin duties as manager and player on Monday as he announced former French captain Philippe Saint-Andre would join from English club Sale from next season to "mastermind" the club's football operations.

Former rugby league star Williams, recruited by Umaga last year, is expected to extend his contract and may now find himself lining up in the centres alongside the 74-Test veteran as Toulon fights to stay up.

Umaga has signed a player contract to the end of the season and Boudjellal said he would continue as manager and work in "close collaboration" with Saint-Andre next season.

"Tana is a natural leader and the team has an enormous respect for him," said Boudjellal, adding that Umaga had been training for two months.

"(He) feels ready in his head ... and will make his return when he's ready."

Saint-Andre's duties would include player recruitment with millionaire Boudjellal expected to take a back seat on football matters next season and concentrate on the club's economic development.

"I said after our defeat to Dax that I was totally responsible for the mistakes in recruitment and that I was searching for a mastermind," Boudjellal said.

"I've found that mastermind: Philippe Saint-Andre."

With the club facing a quick return to second division after just one season in the elite Top 14, personnel has been boosted with the signing of South African five-eighth Conrad Barnard from Super 14 side Cheetahs.

Clermont's France international halfback Pierre Mignoni has also signed a three-year deal while Saint-Andre will bring Sale's French hooker Sebastien Bruno with him to the south of France.

Tongan prop Tonga Lea'aetoa has also joined from London Irish, Boudjellal added.

Umaga guided Toulon into the top flight last year but the team are currently second from the bottom of the Top 14 table despite investing huge sums in high-profile players including Jerry Collins, Joe van Niekerk and Williams.

Saint-Andre, a former France international winger, led Sale to the English championship title in 2006 and the European Challenge Cup crown a year earlier.

He arrived at the English Premiership side in 2004, having previously performed an identical role with Gloucester and in France with Bourgoin.

Saint-Andre won 68 caps for France, 34 of them as captain, and is second in France's all-time try-scorers list with 32, behind Serge Blanco (38).

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