RENTON, Wash. -- In his most ominous comments about the futures of strong safety Kam Chancellor and defensive end Cliff Avril, Seattle Seahawks coach Pete Carroll said Tuesday that both players "are going to have a hard time playing football again" because of their neck injuries.

"The jury's not out on that; they're going to decide that themselves, but it's going to be very difficult for those guys to come back and play again," Carroll said in his weekly radio show on 710 ESPN Seattle.

Carroll described Chancellor's and Avril's situations in more vague terms when he met with the media at large later in the day.

"Honestly I really can't," he said when asked to elaborate on Chancellor and Avril. "I shouldn't say any more than we don't know yet. I don't know. I don't know what to tell you there. Both those guys are marvelous people and competitors and all of that. We'd love to see them through the rest of their career. I don't know what's going to happen there."

Carroll also revealed in his season-ending press conference that cornerback Richard Sherman, who's recovering from a ruptured right Achilles, will have a clean-up procedure on his other ankle/heel area. Carroll said Sherman was bothered by bone spurs "and things like that" and that his clean-up procedure comes with an expected recovery period of four to six weeks.

Carroll said Sherman's recovery from Achilles surgery is "going beautifully."

"He's going to take care of himself to make sure that he's right," Carroll said of Sherman, who turns 30 in March and will be entering the final year of his contract. "That's really important. He's really on the positive side. He's had a tremendous attitude about it. He feels pretty darn good. I think he's out of the boot like this week or something like that. So on goes his progress. I think in the next couple weeks he'll do the other one [surgery]."

Avril and Chancellor suffered season-ending neck injuries a month and a half apart. Avril's occurred in September when he dived to tackle Jacoby Brissett from behind and his chin landed hard on the Colts' quarterback's heel, jarring his neck. Chancellor was injured while making a tackle over the middle in a November game against Arizona.

Carroll has been vague about the specifics of their neck injuries but used the word "stingers" for both. Avril had surgery while Chancellor did not.

Carroll previously said that both players will face decisions about playing again but didn't express as much pessimism about their football futures as he did Tuesday. He answered in the affirmative when asked if it's a quality-of-life issue for both players as they weigh their decisions.

"I think so for both those guys," he said. "Yeah. I think there are concerns."

Chancellor, 29, and Avril, 31, have both been core members of Seattle's defense during the most successful run in franchise history. Chancellor made four Pro Bowls after being drafted in the fifth round in 2010 and signed his third contract with the team last offseason. Seattle signed Avril as a free agent in 2013, the season the Seahawks won their first Super Bowl. He made the Pro Bowl after recording a career-high 11.5 sacks in 2016.

Avril has one more year left on his contract, and Chancellor's extension runs through the 2020 season.

"Whatever those guys decide will be the right thing, whatever direction they go," Carroll said. "They got such great brains and character and all that stuff that they'll make great choices and we'll support them whatever that is."

Carroll said nothing has changed with the status of defensive lineman Malik McDowell, whose football future is uncertain as well. McDowell didn't play a snap as a rookie after suffering what the team described as a severe concussion during a summer ATV accident.

McDowell was Seattle's top draft pick in 2017, chosen in the second round out of Michigan State.

"He had a traumatic accident and it took a big toll," Carroll said. "At this point ... nothing has changed in the evaluation. This young man's future is in the balance of whatever the doctors say and what he can and is capable of doing. We really don't know. At this point, we just have to just wait. I really don't have anything else to offer to you. It's extraordinarily unfortunate to him, as a young man, and it's extraordinarily unfortunate for our organization as well because he's a tremendous prospect and would be a beautiful fit. And if that ever comes back around where that happens, then we'll benefit from it as, of course, he will. But I don't have any information for you that upgrades us from what we know."

Seattle traded for defensive tackle Sheldon Richardson after it became apparent that McDowell would be out indefinitely. Richardson, set to become an unrestricted free agent, has expressed optimism and a desire to return to Seattle. Carroll did the same, saying, "If we could be fortunate enough to get Sheldon back, that would be huge."

Tight end Jimmy Graham is another of Seattle's top pending free agents. Carroll said the two sides have talked about a possible return, adding, "We love Jimmy and we'd love for him to be with us."