Gallen hurt his knee playing for Cronulla against South Sydney two weeks ago and then injured his quadriceps in a boxing session last week, but the Blues skipper confirmed he will play after coming through a run-out against the Melbourne Storm's Under-20 side.
"I trained really good yesterday," Gallen said at a press conference. "(It was) a really strong, really good opposed session (and I) couldn't have done anything else. I woke up fine, no swelling at all and I'm good to go. I'm going fine (and I am) 100%."
Gallen's fitness is a huge boost to NSW, with the Sharks skipper making 31 tackles and 211 metres in their game two win in Sydney last year.
And although Ricky Stuart's side face an uphill battle to defeat Queensland in the series for the first time since 2005, Gallen is confident that the halves combination of Todd Carney and Mitchell Pearce will click.
Carney has starred for Cronulla alongside Gallen at club level this season and will link up with former Roosters team-mate Pearce in a pairing that has Blues fans excited.
"Toddy has been great," Gallen said. "He has fitted in straight into the group and gets on well with everyone.
"His combination with Mitchell Pearce back from the Roosters days is really showing at training.
"The link between the two of them and the speed of the passing is really good between them. He has got to prove himself on this stage. He has got a good opportunity to do it and he is doing all the right things so far."
Gallen was flanked by NSW coach Ricky Stuart and the latter said the Blues camp had avoided the sickness that has ripped through the Queensland camp, with Cameron Smith, Billy Slater and Dave Shillington all under the weather.