Haumono captained Tonga to the final of the Federation Shield

Solomon Haumono has quit the club to make a return to boxing while fellow forward Sione Faumuina has returned home to New Zealand for family reasons.

Skipper Mark McLinden will also miss the start of Super League XII after undergoing back surgery.

The operation was a success but the full-back will miss the first few weeks of the new campaign while he recovers.

"After a great month of pre-season training under Brian McDermott, the squad has been faced with some adversity this week," said Harlequins playing director Tony Rea.

606: DEBATE With the news that Haumono has quit and Faumuina has gone home, I'd say we'll be lucky for top six! ST 606: Have your say

"We have accepted the two players' decisions although, obviously, not pleased by them.

"On the positive side, Mark is recovering well from his back operation and a fully-fit Mark McLinden is terrific news for Quins fans for the season ahead."

The loss of the powerful Haumono, who recently captained Tonga to the final of the Federation Shield, is a particular concern for Quins.

The 31-year-old second-row forward made a big impact towards the end of last season and was tipped to switch to the front row for 2007.

But after two years with the club and with a year on his contract still to run, he has decided he wants to resume his boxing career.

Mark McLinden missed the start of the 2006 season because of injury

The son of former Australian heavyweight champion Maile Haumono, the former Manly and Canterbury player fought eight times between 2000 and 2002, winning all of his contests inside the distance.

Haumono is not the only recent boxing convert from rugby league.

Wakefield captain Monty Betham announced last week he was quitting the game to don the gloves.

As for back-row forward Faumuina, his arrival at the Twickenham Stoop on a three-year deal had been much trumpeted.

The former Canberra and New Zealand Warriors player, who had a spell with Hull FC last season, was expected to give the Quins pack some much-needed firepower.

But after spending several weeks training with his new team, he has announced his shock decision to return home.

McLinden's enforced absence is also a worry for Quins, but the 27-year-old skipper also missed the start of last season.

He was eventually told his back was the cause of his pain but continued to be plagued by problems for the whole year.