NEWPORT Gwent Dragons tighthead prop Ben Castle has been forced to retire because of a back injury, writes Chris Kirwan.

The 32-year-old had to leave the field after just half an hour of September’s RaboDirect Pro12 defeat to Leinster in Dublin.

And Castle, who was out of contract in the summer and was not going to be offered a new deal, has been advised to retire on medical grounds.

He becomes the region’s third front-row forward from New Zealand to hang up their boots this season following the retirements of prop Nigel Hall (Achilles) and hooker Tom Willis (thumb).

"I’m very sad to have finished my rugby career in this fashion," said Castle. "I have thoroughly enjoyed being part of the Dragons, both on and off the field.

"My team-mates and the coaching staff here are a fantastic group of people and I will really miss being part of the set-up at Rodney Parade.

"There are some really talented players here and I know that they have a great future ahead of them."

Castle, who previously played for the Chiefs, Western Force and Toulon, joined the Dragons in 2009 but made just 34 appearances over three seasons after being plagued by injury.

His absence has meant the inexperienced propping pair of Nathan Buck and Dan Way have shouldered a heavy burden this season, with Bedwas’ Keiron Jenkins providing cover. They will soon be joined by Gethin Robinson, who is close to a return after rupturing his Achilles in pre-season.

The Dragons will sign an experienced prop this summer to help develop their young front-rowers next season.