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The Celtics are depending on Al Horford now more than ever

(Maddie Meyer/Getty Images)

Kyrie Irving may be the best player on the Boston Celtics, but the most valuable Celtic on this 2018-19 roster is becoming crystal clear in the second half of the regular season. This team has been living and dying with Al Horford’s minutes, which is a bit of an alarming development as the postseason approaches next week.

Horford was at his best on Monday night, posting his first triple-double as a Celtic (19 points, 11 rebounds, 10 assists) in the midst of an ugly 110-105 win over the Miami Heat. The Celtics won their third-straight game with the starting frontline of Horford/Aron Baynes but were only limited to it for 13 minutes (plus-12) after Baynes picked up four fouls in the first half.

Despite his big individual numbers, the bigger story with Horford was the team’s success with him on the floor. The Celtics outscored the Heat by 10 points in his 34 minutes, signaling a trend that has been constant for the past month and a half. When Horford is on the floor, the Celtics play like a contender (+7.6 net rating). When he is injured or resting on the bench, they play like a team tanking (-11.8 net rating).

No one else on the roster approaches that kind of dramatic split in their on/off numbers. In fact, here’s a closer look at the on/off numbers of Boston’s top players since the All-Star Break for some perspective.

Celtics on/off net rating splits

Horford: +19.4
Hayward: +5.2
Baynes: +4.7
Irving: +2.7

Brad Stevens summed up Horford’s impact perfectly on Monday night after the win.

“I don’t think we can overstate his importance to our team,” he said.

There’s good and bad news on this front as the postseason approaches.

Horford is obviously going to play more once the playoffs hit, which should help a Celtics team that has gone just 9-11 since the All-Star Break. He’s playing a career-low 29 minutes per game this year and his importance on spacing the floor has stood out as Celtics other bigs have struggled on the offensive end. Boston’s offense stalled when he did not play Saturday night against the Nets and the same happened against the Heat’s 2-3 zone when he rested.

“Al is a unique player at the position just for the simple fact that he shoots the ball really well and he shoots the ball really well and he’s not your typical big man where he can just sit in the paint and bang,” Marcus Smart explained. “He can step out and really, really, really stretch out the defense so when he’s not out there teams can just sit in the paint and it’s hard because they clog it up for us.”

“It’s very valuable,” Kyrie Irving added. “Obviously versatility is what makes him very special, being able to play the 4 and 5 spot. But when he’s in that 4 spot, he’s able to facilitate, post up, make great passes, make great plays. It helps us as a team.

When Horford does get into the postseason, his minutes jumped up to 35.7 per game last year, even at age 31. He played phenomenal in the first two rounds against the Bucks and Sixers before dropping off in production against a bigger front line in Cleveland. With Horford’s knee feeling strong amid some planned rest days now, a similar minutes load will be expected this time around but that still leaves roughly 13 minutes per game in which the Celtics will need to find a way to stay afloat without him in the game. In the last 20 games since the All-Star Break, Boston has been outscored by an average of 11 points per 100 possessions when he’s not on the floor. That type of dropoff will be tough to recover from during the postseason.

“We have to play a lot better without him,” Stevens admitted. “Some of that stuff might be sample size, but there’s enough there that we need him. We have to figure out a way to clean it up and play better when he’s not on the floor, and there’s a lot of things that go with that. He’s so good at both ends, and he does everything on the stat sheet.”

Playing Baynes more minutes in general has been a recent shift to help Stevens solve this issue from a defensive standpoint but that is not always a surefire situation as we saw on Monday night. The veteran big man picked up four fouls in the first half, which not only forced Stevens to go with Daniel Theis and Guerschon Yabusele for a short stretch, but also prevented the C’s from playing Horford and Baynes much together for the remainder of the contest against a smaller Heat lineup

The defensive dropoff has been significant whenever Marcus Morris (10 points worse per 100 possessions) or Theis (three points worse per 100 possessions) has been on the floor, while the offense takes a serious nosedive whenever Robert Williams sees action (15 points worse per 100 possessions) in a very limited sample size, mostly due to his lack of shooting range. Those types of splits since the All-Star break understandably gives Stevens plenty of hesitation to play any of those guys at the center spot for long stretches as the postseason approaches, but it also will put an inordinate amount of pressure on Horford and Baynes to stay healthy and out of foul trouble with their added minutes load this postseason.

Danny Ainge failed to address this big man depth issue at the trade deadline and now it’s on Stevens to figure out how to prevent the Celtics from blowing a big lead or digging a hole for themselves in the 12 or so minutes Horford is going to have to rest during the average postseason game. With high stakes games looming against the Heat, Pacers and Magic over the next three contests, it will be a good time to experiment to figure out what the Celtics can get away with it, particularly against a tough Pacers front line.

In the meantime, even at age 32, it’s evident that Horford is the most critical piece to the Celtics success this postseason. Maximizing his minutes on every night will be pivotal to ensure this team’s playoff run goes further than expected after an underwhelming regular season comes to a close.