The New Orleans Saints' decision to place P.J. Williams on injured reserve will end his season, Saints coach Sean Payton said, after the second-year cornerback suffered a severe concussion on Sunday.

Williams, who was hit in the head twice while making a tackle nine snaps into the game — first by the knee of Giants tight end Larry Donnell and then by Saints linebacker Craig Robertson — avoided a spinal injury, but the concussion he suffered will require extended time to heal.

A battery of doctors and experts recommended that Williams miss the rest of the season, although the cornerback is not facing long-term effects.

"He'll be able to make a full recovery," Payton said. "He'll be able to return to football in the offseason, and yet, I would say probably one of the more severe concussions I've seen."

Williams was lying on the field for several minutes while medical personnel from both teams attended. Trainers worked first to make sure he was breathing regularly, and then the medical staff immobilized him before putting him on a cart to leave the field.

"A longer period of time, compared to normal, to what we've seen or what we're used to seeing," Payton said.

Williams' situation is somewhat rare. 

Under the NFL's concussion protocol, most players who suffer a concussion this early in the season have a chance to return to action after passing through the NFL's return-to-participation protocol, which includes rest and recovery, light aerobic exercise, continued aerobic exercise and strength training, football-specific activities, and finally, full football activity.

Typically, players who have suffered a concussion return to action after missing anywhere between one and four weeks; recovery times have gotten longer as the NFL focuses on making sure players are healthy before putting them back on the practice field. 

The injury Williams suffered was so severe that doctors decided it would be better if he take the remainder of the season for rest and recovery.

"It's not measured by just (what happened) on the field," Payton said. "There's a series of tests they do that they're able to determine how much trauma in the event, and his is one where the rest and recovery is going to be necessary. All the experts take a peek at the slides and scans, and so that made the decision to put him on IR an easy one."

Williams spent Sunday night in New York, then returned to New Orleans, and he has been up and walking around the team facility as he recovers, according to Payton.

A third-round pick by the Saints in 2015, Williams was coming into his own before suffering the injury. Williams, who missed his entire rookie season with a torn hamstring, had entrenched himself as a starting cornerback and showed flashes of impressive play in the first 82 snaps of the season.

"I can't speak for him, but I'm sure disappointment to some degree because of the type of recovery, just having gotten into a position where he's competing, playing, starting, and yet, from an encouraging standpoint, none of this will carry over and limit him in any way in the future," Payton said. "He's up and moving around."

Follow Joel A. Erickson on Twitter, @JoelAErickson.