Al Horford is back in the NBA's concussion protocol, dealing blow to red-hot Celtics

After dropping their first two games of the season and losing All-Star forward Gordon Hayward to a horrific leg injury, the Boston Celtics have bounced back in a big way, ripping off nine straight wins to boast the best record in the NBA. Some of that credit belongs to Kyrie Irving, who looks awfully comfortable at the controls of Boston’s offense, and who’s giving more consistently legitimate effort on the defensive end than he ever seemed to sustain in Cleveland.

Some of it’s due to the eye-opening performances of the young tandem of Jaylen Brown and Jayson Tatum, who have stepped into the wing void left by Hayward’s injury with surprising aplomb. And some of it’s due to head coach Brad Stevens, who continues to burnish his reputation as the NBA’s foremost high-rising wizard by pushing all the right rotational buttons to get his young team pulling in the right direction.

[Now’s the time to sign up for Fantasy Basketball! Join for free]

More than anything, though, the Celtics’ scintillating start can be traced back to a defense that’s bigger, longer, more athletic, more versatile and — despite the departures of top stoppers Avery Bradley and Jae Crowder — more effective than last year’s model, ranking No. 1 in the NBA in points allowed per possession. And that can be traced, in large part, to the presence of Al Horford, who has managed to keep Boston’s young greyhounds organized while also handling one-on-one duties against elite scorers like Giannis Antetokounmpo, LeBron James, LaMarcus Aldridge and Kristaps Porzingis.

The Celtics won’t have that back-line safety net when they take on their longtime rivals, the Los Angeles Lakers, on Wednesday night … and they might be without it for a while longer, too.

Horford suffered the injury when he up-faked Kent Bazemore into the air late in the second quarter on Monday night, only for the Atlanta Hawks swingman to come down hard with a left elbow to the head that sent Horford to the deck in a heap:

Horford would stay in the game, playing 33 minutes and finishing with 15 points, 10 rebounds, nine assists and a block in Boston’s 110-107 win. According to the Celtics, the 31-year-old big man didn’t experience any symptoms from the incident until Wednesday morning, at which time they entered him into the league’s concussion protocol.

The league’s policy, put in place back in 2011, mandates that players suspected of having concussions are removed from participation and monitored by team medical personnel, and that those officially diagnosed with concussions are prohibited from returning to play until they can successfully complete the protocol’s return-to-play criteria:

1. He must be without concussion-related symptoms at rest;

2. He must have been evaluated by a physician;

3. He must have successfully completed the NBA return-to-participation exertion protocol, which involves several steps of increasing exertion: from riding a stationary bike, to jogging, to agility work, to non-contact team drills, with the player needing to be symptom-free to move on to the next step;

4. A team physician must have discussed the return-to-participation process and decision with the Director of the NBA Concussion Program, Dr. Jeffrey Kutcher, with the final call coming from the Celtics’ physician.

What might complicate matters here — and what set many of Horford’s fans on edge on Wednesday afternoon — is the fact that he also landed in the concussion protocol following a blow to the head last November. He missed nine games last time around, as his attempts to get back to the court as soon as possible were sidetracked by symptoms he just couldn’t shake.

As the days kept going by, I started to feel worse,” he told the Globe. “Just a lot of things that wouldn’t go away. It was a lot of stuff I didn’t really understand, because it’s never happened to me before.”

“Concussions, you have to be really honest with yourself, and sometimes that’s hard to do,” Horford told Adam Himmelsbach of the Boston Globe. “As athletes, we’re always trained to play through stuff. And I’ve played through all types of injuries — ankle sprains, shoulder, whatever — and with the brain, it’s just different. That was the hard part for me to understand.”

Armed with that understanding this time around, you’d expect Horford and the Celtics to be very careful and cautious in his recovery, recognizing that discretion is the better part of valor when it comes to getting their two-way linchpin back on the court. Nothing’s more important than making sure Horford’s head is on straight, especially after a second head injury, and these Celtics have already proven once this season that they’re capable of withstanding the loss of a major contributor and finding a way to keep rolling.

[Follow Ball Don’t Lie on social media: Twitter | Instagram | Facebook | Tumblr]

But while Stevens has been able to subcontract Hayward’s expected scoring, playmaking and perimeter defensive responsibilities among several secondary options — Brown, Tatum, Marcus Smart, Terry Rozier, second-round rookie 3-and-D fire hydrant Semi Ojeleye — it promises to be more difficult to find a replacement for everything Horford does.

The big man’s off to a killer start this season, averaging 14.6 points, 9.2 rebounds and 4.7 assists in 31.9 minutes per game while shooting 53.1 percent from the floor and a scorching 47.4 percent from 3-point range. He acts as an offensive hub at the elbows and a floor spacer who gives Irving and company more room to work on the interior, while also captaining the defense and serving as an individual stopper; Boston has allowed eight more points per 100 possessions this season with Horford off the floor than when he’s patrolling the paint.

Stevens will have to lean harder on veteran Australian bruiser Aron Baynes and German rookie Daniel Theis, both of whom have gotten off to strong starts in their roles, in Horford’s absence. The longer that absence lasts, though, the more difficult filling the gap will become; Horford’s not Boston’s biggest star, but he might be the most integral element in the schemes that have the Celtics sitting atop the East. Here’s hoping he gets well soon, for the C’s sake and — more importantly — for his own.

– – – – – – –

Dan Devine is an editor for Ball Don’t Lie on Yahoo Sports. Have a tip? Email him at devine@yahoo-inc.com or follow him on Twitter!

Follow @YourManDevine

More from Yahoo Sports:
• Dan Wetzel: Arrested UCLA players released in China, but future is uncertain
• Why won’t the Texans just be honest about Kaepernick?
• Jeff Passan: Roy Halladay was the last of his kind
• Pat Forde: College basketball in state of emergency