Sydney coach John Longmire has lauded his team's "unbelievable effort" in overcoming a 35-point deficit to down Greater Western Sydney after three Swans were withdrawn from the match just an hour before the first bounce.

Callum Mills, Harry Cunningham and Colin O'Riordan were forced out of the clash between the crosstown rivals when they, along with three other Swans players and staff, were re-classified as Tier 2 contacts at the recent Wallabies vs France rugby match in Melbourne.

The Giants lost superstar forward Toby Greene and midfielder Matt de Boer for the match when nine of their players and staff were also re-classified as Tier 2 contacts.

"It was just an unbelievable effort when you consider that we probably had enough reasons just to, if we wanted to, make the choice to not keep going," Longmire said.

"The players' ability to be able to dig in and push against the tide when things weren't going well and recover and go again was outstanding.

"On top of what's already happened, to be able to have the resilience as a footy club to get through and come out the other end of it was just fantastic."

The Swans brought James Rowbottom and Dylan Stephens into the Swans' starting 22 at short notice, with Ben Ronke also added as medical sub.

All three had played in a reserves hit-out the day before the Sydney derby at Metricon Stadium, and were at the team hotel on the Gold Coast when Longmire called them with the news that they would need to back up and play a second game in two days.

Rowbottom, Stephens and Ronke arrived at the ground about 20 minutes before the first bounce.

"We got the medical staff in and went through the players that we thought could back up, and then I rang them and told them to get in the car and come to the ground and get changed," Longmire said.

"They had to quickly get strapped and switch their heads on. And our whole meetings and all that went out the window, so it took us a bit to work it out. 

"The blokes that were told to stay out, they were great too. They kept their energy up even though they would've been flat."