Northampton Saints prop Brian Mujati will leave for Racing Metro at the end of the season.
BBC Look East understands that 28-year-old Mujati is eager for a new challenge and has decided not to take the option of a third year on his Saints contract.
Soane Tonga'uiha, 30, is also close to agreeing terms with the French club.
Saints director of rugby Jim Mallinder told BBC Northampton: "We will be disappointed if those lads go but you can't blame them."
"They've informed me they've received some pretty substantial offers from overseas," he added.
"[We can't compete] unless we were to have about five players in the squad.
"They've done brilliantly for us. I think a lot of credit [should go] to Dorian West and the rest of the players for making them better players.
"If teams come in from France who've got a bottomless pit [of money], and want to buy a front row, that's what they're doing."
It is believed Saints will attempt to bring in London Irish prop Alex Corbisiero as a replacement should the Tongan leave.
England international Corbisiero, 24, is in the final year of his contract at the Madejski Stadium and is believed to be Northampton's top target to replenish their forward line at the end of the season.
Metro expect Tonga'uiha, who has made 192 appearances in six years for Saints, to join them next term, but the Tonga forward has yet to decide whether his future lies in Northampton or Paris.
Zimbabwe-born Mujati, a 12-cap South Africa tight-head, has however signed a deal with the Top 14 outfit and will end a four-year spell at Franklin's Gardens.
Northampton director of rugby Jim Mallinder could turn to versatile prop Paul Doran-Jones to fill the void left by Mujati.
But the 27-year-old former Gloucester forward has a decision of his own to make, with Harlequins and Wasps among the Premiership clubs interested in making an approach ahead of his contract expiry in the summer.
"There's some cracking players out there," said Mallinder. "We've still got a cracking squad.
"What props wouldn't want to play either side of Dylan Hartley. There's plenty of players who'll want to come.
"We'll have a look around and then hopefully, after Christmas, we'll be looking to strike and bring some good players in.
"There's loads of speculation and it's ridiculous to comment. No club can talk to Paul Doran Jones - he's with us until after Christmas, I think he's very happy here and with two props going, there's fantastic opportunities."