He joins Gareth Widdop, James Graham, Tim Lafai and Jack de Belin on the sidelines, with more than half the club's salary cap currently out of action ahead of Sunday's clash with Manly.

Former Bronco Lachlan Maranta will end a 1045-day hiatus from the NRL in place of Lomax who's facing at least four weeks on the sidelines after having a pin inserted in his thumb.

Maranta has spent the bulk of the Canterbury Cup season in the centres and was the only outside back in club's top 30 available for selection other than winger Jordan Pereira.

McGregor admitted it was a tough pill to swallow for his young charge.

"It's an unfortunate one. Right at the back end of training we were doing some basic skills drills and his thumb caught the elbow of Mika [Ravalawa]," McGregor said.

"Unfortunately he's come away from it with a broken thumb so he's going to miss the next four weeks. He's going to get an operation this week, I think it'll be plated.

"I'm not a doctor but the feedback I've got off Zac is that the operation will take place on Monday and there'll be a plate inserted in there and he's looking at a month to recover.

"It adds to the collection of guys on the sideline but Lachlan Maranta will get an opportunity this weekend. We're looking forward to seeing how Lachy goes.

"He's been working hard in the lower grades and at training to get an opportunity, he's got that now so it's over to him."

It also leaves the Dragons without a goal-kicker for Sunday's showdown, with Lomax now sidelined alongside Widdop and Lafai. Corey Norman and Jacob Host are part-timers with the former likely to get the nod to start Sunday's match.

Jai Field will assume kicking duties while ever he's on the park but has typically played minimal minutes when used as a bench weapon.

The Dragons aren't alone in battling the toll. The Sea Eagles having gone long stretches of the season without the likes of Tom Trbojevic and Daly Cherry-Evans.

It's part of the most injury-plagued NRL season in recent memory, with McGregor saying he can't recall a time, as a player or coach, where depth has been so tested.

"I haven't witnessed it throughout the time I played for 11 years as well as coached but we play a contact sport," McGregor said.

"It's part of the game, we've got to move on. There's no excuses. We've got to get on with the job which is to go up to Brookie and put in the best performance we can."

McGregor had named the same 17 that got back in the winners' circle against Canterbury last week and said the overall mission remains the same.

"For us it's about maintaining certain standards in our game," McGregor said.

"If we live by and play to those standards we'll get the wins we need to. In the last month we've played some good footy but we haven't played a complete game.

"On the weekend we were very close but we didn't do it either. We got a result but this week the focus is solely on Manly. We've got a 12-day break after that so it's about leaving everything out there."