WALTHAM, Mass. -- One week after Boston Celtics big man Al Horford suffered a concussion during an off-day practice, coach Brad Stevens said the 10th-year veteran has not progressed in the NBA's concussion protocol and he is uncertain when Horford will return to basketball activities.
Horford, who signed a four-year, $113 million contract with the Celtics over the summer, has missed Boston's past three games. The concussion was diagnosed Tuesday, after he experienced nausea while attempting to practice a day after absorbing an inadvertent blow to the head from a teammate.
"[Horford] has not advanced in the protocol, based on what I've been told," Stevens said after Monday's practice. "I have not gotten anything deeper than that, but he did not do anything with our team today."
On Saturday, Horford could be seen running on a treadmill above the Celtics' practice court with team trainer Ed Lacerte monitoring the session. Horford then engaged in some light on-court work but quickly departed.
Stevens had said that if that session went well, the team would increase Horford's activity. Instead, his status for Wednesday's game against the Washington Wizards is uncertain, with the Celtics set to fly to the nation's capital Tuesday afternoon.
According to the NBA's 2016-17 concussion protocol, a player cannot return to team activities until:
• He is without concussion-related symptoms at rest.
• He has been evaluated by a physician.
• He has successfully completed the NBA return-to-participation exertion protocol.
• A team physician has discussed the return-to-participation process and decision with Dr. Jeffrey Kutcher, director of the NBA concussion program. The final return-to-participation decision is to be made by the player's team physician to maximize the consistency of care for the player.
Stevens said that Saturday was Horford's first day attempting to navigate the return-to-participation checklist, about which the league notes:
• The return-to-participation protocol involves several steps of increasing exertion, from a stationary bike to jogging to agility work to noncontact team drills.
• With each step, a player must be symptom-free to move to the next step. If a player is not symptom-free after a step, he stops until he is symptom-free and begins again at the previous step of the protocol.
• There is no time frame to complete the protocol.
It would appear that Horford was unable to advance beyond jogging during Saturday's activity. He was not spotted after Boston's practice Monday.
The Celtics are 3-3 overall and 1-2 since Horford's injury. Boston's biggest area of concern without Horford has been defense. With Horford on the court this season, the Celtics have an excellent defensive rating of 99.7 in the 88 minutes he has played. That rating spikes to a cringe-worthy 114.9 without him. Boston, which tied for fourth in defensive rating last season, ranks 29th this year at 110.2 overall.
Struggling to rebound this season, regardless of whether Horford is on the court, the Celtics have started Tyler Zeller in his place the past three games. Stevens said the team would consider starting lineup changes before Wednesday's game but said that might hinge on who is available.
"I don't know what we're going to do Wednesday," Stevens said. "We've got a couple of days now to think about that. [Monday] was more about, let's assess and watch what we didn't do well and what we did do well, which on [the defensive] end of the floor wasn't much, and then figure that out. And I don't know who's going to be available, so that's the other part of that equation."
The Celtics have yet to be at full strength this season. Boston is currently without two starters in Horford and forward Jae Crowder (ankle). Also, top bench option Marcus Smart missed the first three games of the season with an ankle injury, and backup big man Kelly Olynyk has yet to make his season debut after undergoing shoulder surgery in mid-May.
Olynyk could be back soon -- though he has remained hesitant to offer a firm timeline other than saying he's "real close" -- while Crowder said Sunday that he expects to be out a week or two and will not rush back after pushing himself too much late last season and struggling in the playoffs.