Cronulla coach Shane Flanagan has backed up his captain's comments regarding players leaving the game while under contract following the departure of star fullback Valentine Holmes.

Holmes has been granted a release from the final year of his deal in order to pursue a career in the NFL.

On Tuesday, Sharks skipper Paul Gallen said the league ought to consider bans for players who don't honour their contracts and leave the game.

Speaking on The Rush Hour with MG on Triple M on Wednesday evening, Flanagan said he agrees with Gallen's take.

MORE: Cronulla Sharks eye Shaun Johnson as Valentine Holmes replacement

"Gal always speaks from his heart and his emotions get to him sometimes, but I fully support what he's saying," Flanagan said.

"It's his last year in the NRL and he planned to have Val as his fullback and he wanted Val to be part of his last year and all of a sudden for Val to say 'I'm going to the NFL,' it doesn't sit well with Gal and I really appreciate that and I can understand that."

Flanagan, who coached the club to its inaugural premiership in 2016, said he wouldn't be opposed to the league intervening in situations such as this one.

"The hardest thing for us is that he has got another year on his contract... and the timing of it is poor - we're into a pre-season and our best player is leaving," Flanagan said.

"I just think it's sending out a poor message. If you sign a contract you should try and honour it at least.

"If you go and you're under contract, don't expect just to walk straight back in.

"If we have that hanging over their head, that you might be gone for two years, maybe they mightn't go in the first place. I think we need to look at it."

When news first broke of the 23-year-old's departure, Flanagan said he wanted to speak to the Queenslander about his decision.

The coach has since caught up with Holmes and gained an understanding of the move, though he was still frustrated at the timing.

"I spoke with Val today for a good hour or so," Flanagan said.

"I understand his position. It didn't come out the way he wanted it to. The media got a hold of it before he got to speak to the playing group and so on.

"So I'm a little bit more aware of the circumstances and how it unfolded.

"He knew he had his contract here, that's the disappointing thing.

"We were thinking he was going to go to Townsville in 2020 and we were preparing ourselves for that.

"The shock of him all of a sudden coming to us and telling us 'I'm even not going to Townsville, I'm going to the NFL in 2019' was the hardest thing to get a hold of.

"I want him to follow his dreams but also I want him to stay here and play football for the Sharks.

"It's been a real journey with him and I don't really want to let him go. I just want to say 'no, you're not going mate, bad luck'."