BOSTON — Boston Celtics big man Robert Williams didn’t respond well to the initial phase of the return-to-action concussion protocol and reverted to the beginning stages Friday, according to coach Brad Stevens.

Williams spent time on the treadmill with team trainers after sitting out Friday’s practice and the team will wait to see how he reacts. Williams was placed into the league’s concussion protocol after absorbing a Kevin Love elbow to the head during Tuesday’s preseason finale in Cleveland.

“Rob is, I think you can see where he’s at, he’s on the treadmill. He didn’t feel great after [Thursday’s work] so they dialed him back, so he’s back to Day 1 again," said Stevens. "We’ll see how he feels after today. That’s kind of the way that progression works. So he’s at the early stages of it.”

The better injury news for Boston was Romeo Langford returned to non-contact drills Friday. He had sidelined since slipping on the court and spraining his knee in Sunday’s exhibition win over the Cavaliers.

Stevens said Langford could return to full-contact practice as early as Monday.

Said Stevens: "Romeo actually did some of the non-contact portion of practice today, moving pretty well. He looks pretty good.”

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