A brutal attack during a sevens rugby game in Upper Hutt over the weekend left a promising young player in hospital with serious facial injuries and his family pressing assault charges with police.

Ridge Studd was playing for Petone against Marist St Pats (MSP) during Wellington Rugby's annual American Ambassador's Sevens tournament at Maidstone Park on Saturday.

One of Studd's teammates is understood to have used an elbow on an MSP player, provoking a response from the opposition.

When Studd attempted to intervene, he was punched, knocked to the ground unconscious and suffered a seizure. Even then, it's alleged his assailants continued to punch and kick him.

The 18-year-old was left with numerous fractures around his eye socket, severe swelling and a serious concussion.

Three MSP players were sent off and the club was disqualified from the tournament while Petone elected not to continue. A number of Studd's teammates accompanied him to hospital, along with his mother, who watched events unfold from the sideline.

An eyewitness (himself a senior player from another club) told the Herald Studd was hit from behind and attacked while he lay on the ground.

"It was the most vicious and dog-pack-mentality act I've seen in any game ever," he said.

"It was honestly the most disgusting thing I've ever seen in rugby."

On the club's Facebook page, Petone chairman Wayne Smith told members Studd was discharged from Wellington Hospital after being checked over and having CT scans.

"His eye was damaged but thankfully he is expected to regain sight," he said.

"While emotions have been running high we ask everyone to leave (the) matter to the appropriate channels. The Petone Rugby Club and the Studd whanau would like to thank everyone for the many texts and calls received from concerned people. We also appreciate the support shown from fellow clubs. Kia Kaha Ridge."

Wellington Rugby CEO Matt Evans said the union has offered support to the family and the clubs involved. He said Petone and MSP were fully cooperating with the police and WRFU would reserve further comment until the investigation was complete.

"We strongly condemn any form of violence in our game and are extremely disappointed anytime something like this occurs. Our immediate thoughts are with the injured player and ensuring he has the necessary support around him as he recovers from his injuries," said Evans.

MSP chairman Rob Evans said his club would wait for the official judicial process to play out before deciding on any further action it might take.

Evans said the thoughts of everyone at the MSP club were with Studd and his family and that some of his side's players had visited Studd the day after the attack.

Studd was 2019 deputy head boy at Wellington College and won the award for outstanding all round Year 13 student. He captained the school's first XV, represented Wellington at age-group level and was last year selected for a national under-18 Maori Development Camp.

He is an apprentice plumber and played for the Petone Colts side in the 2020 winter season. The injuries he suffered have left him unable to open his injured eye and with constant headaches, meaning he is unable to work.

Three players from MSP and one from Petone have been stood down from all rugby activity pending the results of the WRFU's judicial process.