Jim Mallinder has confirmed Samu Manoa is negotiating with French clubs and is likely to leave Saints next summer.
But he says nothing is set in stone as yet and has stressed rumours surrounding Dylan Hartley and George Pisi remain speculation.
Manoa has been heavily linked with Toulon in recent weeks, with reports in France suggesting the America star is close to signing a two-year deal at the Top 14 champions.
And Mallinder admits Saints can’t afford to compete with the cash-rich clubs from across the Channel.
“He’s going to be sought after, is Samu,” the director of rugby said. “I do know the speculation is right, there’s massive interest from France.
“There’s a number of clubs who are really, really after him. I spoke to him and it’s more than likely he’s going to go to France.
“We’ve got our salary cap, we’d love to keep him, but there comes a point where you’ve got to say ‘well done, thank-you for what you’ve done here and let’s make sure we have a good season’.
“He’s got to make his own mind up, he’s doing that. There are a number of French clubs who will be willing to pay a lot of money for him.”
Saints skipper Hartley has been linked with a move to Montpellier, while Samoa centre Pisi is reported to be a target for Castres.
Mallinder accepts that his double-winning squad will attract interest, but also feels his club are a big pull for players as he continues to look at recruitment.
“It’s all speculation, I wouldn’t just say it’s Dylan, it’s George,” he said.
“We’ve got some quality players and worldwide people want quality players, which puts a price on their head, but we’re very comfortable where we are, we don’t discuss how our personal negotiations are going.
“They are ongoing with our current squad and also with other players from other clubs. We’re always looking at our recruitment and we’ll continue to do that.”