(The Sports Xchange) - Denver Broncos safety Darian Stewart and linebacker Brandon Marshall were fined by the National Football League (NFL) on Wednesday for hits on Carolina Panthers quarterback Cam Newton.

The fines came one day after the NFL's director of officiating, Dean Blandino, offered an explanation for Newton taking multiple helmet-to-helmet hits -- it's all about his posture.

Stewart was fined $18,231, sources told ESPN, for his helmet-to-helmet hit on Newton that came with just under 40 seconds remaining in the Broncos' 21-20 victory over the Panthers in last Thursday night's NFL season opener.

Stewart was called for roughing the passer, but Newton also was flagged for intentional grounding on the same play, meaning there were offsetting penalties.

Marshall's hit in the third quarter was not called a penalty, but he was fined $24,309 for impermissible use of a helmet, ESPN reported.

Blandino said on Tuesday he believed one penalty had not been flagged for a hit on Newton that should have been called.

Blandino likely was talking about Marshall's hit when he launched himself into Newton, hitting the quarterback in the helmet.

"We reviewed all of the hits in the game, just like we do for every other game," Blandino said on Tuesday's edition of NFL Total Access, "and there was one call that we felt was missed."

The NFL and the NFL Players Association each said earlier in the week they are investigating the response by medical personnel during the game after Newton absorbed multiple hits to the head.

Newton's father, Cecil Newton, said the family was "grossly disturbed" by the repeated shots his son absorbed in Week One.

Broncos coach Gary Kubiak defended his players against criticisms that the team is playing "dirty."

"I disagree," Kubiak said on Monday. "We play hard, we're going to continue to play hard."

Panthers coach Ron Rivera said the 6-foot-5, 245-pound Newton, the reigning MVP of the NFL, is not being treated like someone of that stature.

"I think there is a little bit of prejudice to that," Rivera said of the lack of penalties. "It's kind of like Shaquille O'Neal.

"He's a big, physical basketball player and he goes to set a pick and they fall down and they call a foul on him. Then he goes to shoot a layup and gets hacked and hammered and they don't call it."

Blandino said quarterbacks lose protection when they transition from passing threat to running threat.

"It's basically the posture will dictate his protection," Blandino said. "So if he's in running posture, ball tucked, advancing it as a runner, he's treated like a runner and he doesn't get special protection.

"If he's in a passing posture, whether he's inside the pocket/outside the pocket, he's still going to get passer protection - head, neck, crown to the body - those types of protection. So it's the posture that dictates the protection."

Blandino was asked about the offsetting penalties - the helmet-to-helmet hit and intentional grounding - being called late in Thursday night's game despite heightened concussion awareness.

"That's the rule," Blandino said. "If it were a 5-yard penalty on the offense, say it was an illegal formation or an illegal shift, that 5-yard penalty would go away and only the 15-yard personal foul would be enforced.

"But if it's a 10-yard penalty or a foul like grounding, the fouls offset."

(Editing by Mark Lamport-Stokes)