Adam O'Brien says he overruled Kalyn Ponga and sat Newcastle's captain out of their 20-6 NRL loss at the hands of St George Illawarra for his own good. O'Brien said he took the decision out of Ponga's hands after the Knights fullback played for Queensland in the State of Origin opener on Wednesday. The Newcastle captain has been carrying an ankle ailment for the past three weeks and was ruled out of Friday's game at Jubilee Oval an hour before kick-off. Without their captain, Newcastle lacked spark and they didn't cross the line until the 70th minute when edge forward Kai Pearce-Paul crashed over, as Clint Gutherson led the Dragons to a comprehensive victory. "He was doing everything he could (to play), I took the decision away from him because it's the right thing to do," O'Brien said of Ponga. "It's the type of injury that takes a few days to settle down. Two days is not enough. "He's disappointed, a little bit angry with me but again we've got to protect him." O'Brien said the NRL's scheduling had added to Newcastle's woes after they were kept scoreless in a first half for the seventh time this season. The Dragons led 18-0 by halftime and could have been accused of failing to turn the screw against a Knights side lacking direction. Jaydn Su'A got the Red V rolling with a 20th minute try before the would-be Queensland back-rower succumbed to an ankle injury. But it didn't knock the Dragons off course, with Shane Flanagan's pack finding plenty of joy up the middle. First a rampaging Jack de Belin run was the catalyst for the workaholic captain Gutherson to cross before Damien Cook sent man mountain Loko Pasifiki Tonga over for his first NRL try. "We took our opportunities when we needed to, and defended well - we only missed two tackles in the first half," Flanagan said. "The second half was going that way. It was a bit of an arm wrestle, and then we get on top of them." The Dragons added a second-half penalty through Valentine Holmes and should have added more tries only for Holmes and Tyrell Sloan to drop balls over the line. Pearce-Paul crashed in for the Knights' only score of the evening with 10 minutes left. Rugby sevens convert Nathan Lawson made his NRL debut for the Dragons and didn't look out of place by chalking up 176m from 17 carries on the left wing. "He's just that type of personality, I don't want to play him down at all - he's not a flashy type of player, he's a real tradesman," Flanagan said. Flanagan was confident Su'A's injury would not be a long-term issue but the ankle complaint will likely deny the edge forward a chance at a Queensland recall.