Canberra have bolstered their NRL stocks significantly on Tuesday with the signings of Melbourne forward Lagi Setu and Warriors winger Bill Tupou.

But that news was soured somewhat with confirmation prop Brett White will spend at least two weeks on the sideline with a fractured eye socket.

Lagi will join the Raiders on a two-year deal starting next season.

Raiders boss Don Furner said Setu would be an adequate replacement for St George-Illawarra-bound Joel Thompson.

"Lagi is a fine young player and will be a perfect replacement for Joel Thompson," Furner said.

"We actually tried to sign him four years ago, but he returned back to Brisbane and then headed off on his two year Mormon mission. We are very happy to have secured him the second time around."

The Raiders are yet to confirm the acquisition of Tupou, but the 22-year-old's manager Stan Martin told AAP his client has been granted an immediate release from the Warriors and will join Canberra next week on a two-and-a-half year NRL deal.

On Monday Canberra also signed former Gold Coast Titan Jordan Rapana until the end of 2014 in a move to bolster the NRL club's outside backs depth.

Winger Edrick Lee (broken arm), centre Blake Ferguson (deregistered over alleged indecent assault charge) are long-term absentees out wide for Canberra, while Tom Learoyd-Lahrs, who had surgery on a ruptured tendon in his foot, is now back training at the gym.

Former NSW prop White picked up the injury in Saturday's loss to the Wests Tigers at Campbelltown Stadium, but will not require surgery.

"Disappointing news last night. Fractured eye socket. Out for 2-3 weeks", White posted on Twitter after having scans.

Melbourne said salary cap pressure meant they were unable to re-sign Setu and also confirmed Junior Sau's departure to Super League club Salford at the end of the year.

"It was the club's and both Junior and Lagi's preference to remain with Melbourne Storm, however due to salary cap constraints and other circumstances we were unable to offer them a position on our playing roster for 2014," Storm football manager Frank Ponissi said.