Former Wallabies captain David Pocock and prop Ben Alexander are the next re-signing targets as coach Stephen Larkham tries to find a way to keep the core of his squad together.

Mogg and Nic White have signed with French club Montpellier, joining former Brumbies coach Jake White and captain Ben Mowen.

Mogg's departure has been partly offset by the retention of Robbie Coleman, who has a new two-year deal with the Brumbies after turning down an offer from cross-code rivals the Canberra Raiders and a chance to play Sevens for Australia at the Olympic Games.

It's understood second-rower Jordan Smiler and Fotu Auelua will also leave the Brumbies at the end of the season, while hooker Siliva Siliva has already signed with the Melbourne Rebels for 2016.

Larkham is working to re-sign a host of players, including Alexander and Pocock, as he fights off the lure of big-money offers in Europe and Japan.

It's understood Mogg's offer from France was twice what he would have been earning in Canberra.

"We would have liked to have kept both Moggy and Robbie, but in the end we couldn't," Larkham said.

"The lure of Europe is always going to be there, keeping a squad together for more than three years is always going to be difficult.

"You build them up and then can't afford them [in the salary cap] and they get opportunities to go elsewhere. It's the cycle of the game that you have to be aware of.

"We're lucky enough to have retained the majority of our core players."

Coleman has been weighing up potential career changes in recent months. The Raiders came knocking with an offer to switch to the NRL, given Coleman played junior rugby league with Josh Dugan.

The Australian sevens team also expressed interest as they target the Rio Olympics next year.

Coleman never seriously considered the Raiders offer and chose to put the Brumbies ahead of Sevens ambitions.

"I can understand why people were chasing him," Larkham said. "It would have been devastating if we lost both of them [Coleman and Mogg]. I certainly understand Jesse's point of view with his opportunity."

Jake White is building the French version of the Brumbies, with Mogg, Mowen and Nic White now on Montpellier's books.

An emotional Mogg told his teammates on Thursday he was leaving. While it is common for Australian veterans to move abroad, White and Mogg leave while still in the early stages of their careers.

Mogg, 25, hasn't ruled out an Australian rugby return in the future, but admitted limited opportunities to progress into the Wallabies squad influenced his decision.

"With only five games left and having not played much this year, it was hard to push my case for a contract at any club," Mogg said.

"I spoke to Jake and I had to make a decision, I didn't want it to linger on. I made the decision, I don't regret it. I'm content."

Mogg has missed the majority of the season with a shoulder injury, but will continue his comeback at fullback against the Cape Town Stormers on Sunday morning. He conceded Israel Folau's form had all but ended his World Cup dreams.

"Izzy has that locked down. Could I break into the team on the wing? Probably not," Mogg said.

"Maybe something on the bench, but that's fairly slim. My intentions were to get back into the Test team, but the World Cup was a long shot."

SUPER RUGBY ROUND 13

Sunday: Cape Town Stormers v ACT Brumbies at Newlands, 1.05am. TV time: Live on Fox Sports 2