Former NRL star, 34, is sentenced for intimidating staff and throwing a rock through a window at a boutique boxing gym where he once worked

An ex-NRL star has admitted to throwing a rock through a window of a boxing gym he once worked at as well as intimidating staff.

Daniel Conn, 34, who once starred for the Canterbury Bulldogs, Gold Coast Titans and Sydney Roosters faced charges from three separate instances at the Hustle Boxing gym in Potts Point in Sydney.

Conn pleaded guilty to intimidation and stalking, destroying property and breaching an AVO, and on Friday was sentenced to an aggregate 14 month conditional release order.

Daniel Conn has pleaded guilty to damaging property and intimidation at the Hustle Boxing gym he used to work at in Potts Point in Sydney

Daniel Conn has pleaded guilty to damaging property and intimidation at the Hustle Boxing gym he used to work at in Potts Point in Sydney

Conn had quit working at the boutique gym last year and on December 8 he threw a rock through one of the glass windows, the Downing Centre Court heard.

Within days he returned to the gym only to be told by an employee he 'wasn't welcome', The Daily Telegraph reported.

The 34-year-old then shouted: 'You don't know what you've done, you don't know what will happen next'.

The owner of the Hustle Boxing gym then took an AVO out against Conn, which banned him from being within 100 metres of the fitness centre.

The retired NRL player then drove past the gym on a scooter on December 19 and waived to those inside.

Conn on Friday said he would cover the $4,520 cost of the broken window.

Magistrate Michael Antrum took into account that Conn had been receiving help for mental health issues but condemned his behaviour towards the gym's staff.

The 34-year-old had also starred on the hit reality show Geordie Shore with Vicky Pattison

The 34-year-old had also starred on the hit reality show Geordie Shore with Vicky Pattison

The pair briefly dated after Conn appeared on the show as a personal trainer while the cast filmed in Australia in 2013

The pair briefly dated after Conn appeared on the show as a personal trainer while the cast filmed in Australia in 2013

'We live in a generally peaceful community and while a boxing gym may not be an obvious target for intimidation, all persons are entitled to attend a workplace without fear of intimidation,' he said. 

The conditions of Conn's release order means he must pay compensation to the gym as well as continue mental health treatment.

The 34-year-old retired from the NRL in 2011 and became a personal trainer.

He also featured on the hit reality show Geordie Shore in 2013 and briefly dated star Vicky Pattison.

Conn was also once the face and global athletic director of the F45 fitness chain.

Recently the ex-footy star opened up about his struggles with depression and his attempts at taking his own life.  

Conn starred for the Sydney Roosters before retiring from the NRL in 2011 (pictured in March, 2010)

Conn starred for the Sydney Roosters before retiring from the NRL in 2011 (pictured in March, 2010)