FRISCO, Texas -- The Dallas Cowboys have placed Pro Bowl center Travis Frederick and veteran wide receiver Terrance Williams on injured reserve and activated defensive tackle David Irving from the suspended list, the team announced Saturday.

With the moves, the Cowboys have 52 players on the roster.

Frederick has been battling the effects of Guillain-Barre syndrome, an autoimmune disease that affects the nervous system, since training camp. The Cowboys opted to keep him on the 53-man roster at the start of the season, keeping open the possibility of him playing sooner than many expected.

By being placed on injured reserve now, Frederick would not be able to play again until December, but the reality is there is no timetable as to when he can return. Frederick said he has made improvements, but they are more incremental than dramatic.

Williams would also be eligible to return in December, but he is facing a potential suspension from a May arrest for public intoxication. Williams missed the last week of practice as he dealt with what coach Jason Garrett called off-the-field issues as well as a foot injury. He missed a game for the first time in his career last week and saw his playing time decrease dramatically in the first three weeks of the season.

Williams missed the offseason program, organized team activities and June minicamp because of foot surgery. He was able to take part in training camp and was not on the injury report before this week. He had just two catches for 18 yards in three games.

The Cowboys signed veteran Brice Butler as insurance two weeks ago with Williams' potential suspension looming, but had seven wide receivers on the 53-man roster.

The Cowboys re-signed Williams to a four-year, $17 million deal last year as a free agent that included $9.5 million guaranteed. Williams' $3.5 million base salary was guaranteed entering the season.

Irving was suspended the first four games of the season for violating the substance-abuse policy. He practiced Wednesday but tended to family issues on Thursday and Friday, and will not play Sunday.

It was Irving's first practice since last November after missing the final four games of the 2017 season because of a concussion. He was not around the team much in the offseason and was on the did-not-report list during training camp, working out at a gym in Hollywood.

Frederick said he has improved after being diagnosed with Guillain-Barre during training camp. Initially, Frederick thought he was dealing with stingers because of the weakness and tingling feeling he had in his arms. When his strength did not return, he underwent more testing, which determined he was dealing with Guillain-Barre.

Frederick spent a few days in a hospital and underwent intravenous immunoglobulin therapy to aid his immune system.

He has been working out and taking part in meetings, and has been at every game. In September, Frederick said the process has been difficult.

"When you're injured, you try and get past it. This is something I can't just will my way through," Frederick said. "It's a matter of the nerves not conducting properly and not working correctly. It's going to require some patience and some great work from our rehab staff and our strength staff to be able to just continue push forward and take what my body gives me so I can continue to improve as those things come back, and then I hopefully I can take that bigger jump."

Long-time NFL lineman Mark Schlereth said he needed more than a year to feel 100 percent again after dealing with Guillain-Barre in the 1990s while playing for the Washington Redskins.

Frederick has been named a Pro Bowler in the last four seasons and never missed a game before this year. He said in September he has not thought about retirement.

"Right now my focus is getting back to being here and being able to play again," Frederick said. "It's a matter of time for that to happen, and unfortunately, I don't know what that time is. I think as long as I continue to keep my eyes forward and continue to work toward that, we're going to be in good shape."