Best suffered a groin complaint during Saturday's thrilling 30-28 win over the Dolphins in Perth, while Saifiti went off with a hamstring injury.
Lock Adam Elliott is also under an injury cloud.
Knights coach Adam O'Brien says the trio will be assessed before a call is made on their availability.
"Jacob's got a low-grade hamstring, and Bradman Best has got some groin tightness," O'Brien said.
"And I think Adam Elliott - we're a little bit knocked around.
"So we'll front load their recovery over the next few days and we'll see."
Best has been in hot form this season.
When asked whether the NSW Origin newcomer is in any doubt for the Bulldogs game, O'Brien replied: "Potentially, just the way he pulled up."
"I don't think it's anything too, too serious. But we'll just see over the next 72 hours how they've pulled up recovery wise.
"We've got a long flight obviously. So we'll get through all that."
The Knights have soared from 14th into the top eight on the back of a five-match winning run.
Star fullback Kalyn Ponga helped mastermind the win over the Dolphins, with his scintillating runs setting up two second-half tries.
"I thought when we needed something in the second half to get us out of jail, he was one of the guys that provided that for us, no doubt," O'Brien said.
The Knights have beaten the Bulldogs, Wests Tigers, Storm, Raiders and Dolphins during their winning run.
Although the win over the Dolphins wasn't pretty, O'Brien said it was a good sign that his team was able to grind out the win.
"I am rapt to get the two points," he said.
"I don't think we played particularly well.
"There were some moments in the game that we'd like to have back.
"The team has been performing at a pretty high level for the last probably four or five weeks .
"We did anticipate that there would be a game that you're not quite at your best, but fortunately they managed to fight their way back and get the two points.
"You'd rather get your lesson and the two points (than lose), so that's probably where we're at."
The Knights beat the Bulldogs 66-0 when they met on July 2, with that result kick-starting Newcastle's winning run.
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