Cowboys players sent messages of support to Macdonald before returning to pre-season training on Monday after it was revealed the speedster was struck on the head by a bottle at a Port Moresby hotel on Saturday night.

Macdonald, who starts Cowboys training on December 5, was hit while celebrating with PNG Kumuls teammates after their weekend win over England Knights development team.

The Kumuls said police were investigating the incident.

A Cowboys spokesman said Macdonald had recovered and was flying back to Australia.

Cowboys forward Mitch Dunn said the Macdonald incident was a shock to the players before North Queensland officially began life without retired great Johnathan Thurston at their first pre-season session on Monday.

"A few of the boys have spoken to him, hopefully he can move on," Dunn said of Macdonald.

"We are looking forward to having him here. He has that X-factor, he scores tries that no one else can."

Macdonald took to social media to assure concerned fans on Sunday night.

"Thanks everyone for the messages and concern," he posted on Facebook.

"I am fine and just disappointed last night ended the way it did after a good win for the Kumuls with unnecessary violence. Thanks to all the Kumuls fans for all the support."

The Kumuls demanded a "thorough" police probe.

"The Papua New Guinea Rugby Football League has been made aware of an incident involving a PNG Kumul player on Saturday night in Port Moresby," a PNGRFL statement said.

"PNGRFL CEO Reatau Rau said the PNGRFL will request the Police Minister and his department to carry out a thorough investigation into this incident.

"The PNGRFL will issue a statement as soon as the facts have been established."

Australian Associated Press