With Celtics' defense slipping, it's time for more Aron Baynes

Al Horford is not his usual self this season, a fact that has been evident for weeks even before his knee injury became public back in November. While Horford’s scoring efficiency has been better over the last month since taking eight games off to rest his runner’s knee (18 points in Friday’s 122-116 win over the Grizzlies), the 32-year-old is clearly not where he was last year from a defensive standpoint. The Celtics were better on defense last year when Horford was on the floor, but as he has slid into a full-time starting spot at the center, the dropoff has been considerable (team allows four more points per 100 possessions when he plays this season).

Some of that dropoff has been due to his age and reduced mobility due to his knee, but there has been another underlying factor in his struggles: He hasn’t been paired with one of the best big men defenders in the league nearly as much.

Through 44 games entering Friday night, Aron Baynes (six points, season-high 12 rebounds in 22 minutes on Friday night) and Horford had played together for just 38 minutes over nine games. That’s roughly 11 percent of the total Horford and Baynes had played together at the halfway point last season (319 minutes).

There are reasonable explanations for that dropoff. Horford (nine games) and Baynes (18 games) have missed more games than anyone else in the Celtics rotation while healthy. Brad Stevens has opted for more small-ball based lineups as well in order to create more minutes for the likes of Gordon Hayward, Marcus Morris and Jaylen Brown.

Still, there’s no denying that 38 minutes in nine games is an absurdly low number for one of the best defensive duos in the league last season. Horford and Baynes allowed 95 points per 100 possessions last year, a number that was the lowest among regular duos (300-plus minutes) on the Celtics roster. This year?

In a limited sample size, they’ve been even better, allowing just 93 points per 100 possessions over nine games.

With Baynes back healthy, Stevens acknowledged on Friday night that he is considering a shift on that front.

“We’re looking to try to get ways to play those guys together a little bit more,” Stevens said. “That’s something that you might see a little bit tonight. Certainly might see beyond tonight. Just because, I think, everybody benefits from Baynes and I think that it allows Al to post a little bit more. That allows Al to guard 4s, not have to bang as much. Baynes takes a lot of weight off of everybody’s shoulders. They didn’t play together the other day, but hopefully we’ll see that lineup some, probably not en masse but some at least.”

Grizzlies coach J.B. Bickerstaff also spoke about the impact Baynes has on a regular basis that makes him a challenge to play against.

“I think the physicality that he plays with,” he said. ‘Obviously his ability to protect the paint and impact the paint on the offensive end of the floor as well. He’s physical, he offensive rebounds, so now it puts more pressure on your defense to finish possessions. And then defensively he’s crafty, he’s smart, he’s always in the right place at the right time.”

After keeping Baynes and Horford separated throughout the first half (an ugly one in which C's allowed 62 points), Stevens finally gave in after the break, playing the duo for eight minutes together, including a large chunk of crunch time. Boston slowed down the Grizzlies offense just enough in that stretch to come out with a 122-116 win, outscoring the Grizzlies by ten points over those eight minutes.

“I thought he was really good," Stevens said of Baynes. "I thought again the bench came in that first quarter and did a great job of getting us a lead, and then – and then we didn’t play very well in the last eight minutes or so of the second quarter – and then, you know, early on in the third it was kind of going back and forth and we just kind of decided that it’s better to be big against these guys as much as we could. And, you know it’s the first time we’ve played Al (Horford) and Baynes together. We’ll probably see more of that as the time goes on because it – Baynes gives you such a defensive presence and he was good on the glass offensively as well.”

The limitation on playing Baynes with Horford in the past had always been due to floor spacing, at least on the offensive end. However, a Baynes rectified that issue during last postseason, to the point where opposing bigs have to at least respect him a bit to contest him on the perimeter thanks to his improved 3-point shot.

While it’s tough to play Baynes against teams that like to go small at the four spot, there are still plenty of squads around the league that play a pair of traditional bigs at times, such as the Grizzlies. Memphis nearly did it for the entire game on Friday night, playing two of Marc Gasol, Jaren Jackson Jr., JaMychal Green and Joakim Noah for the better part of 48 minutes. Still, Stevens elected not to have Horford and Baynes share the floor together at all in the first half on Friday before finally giving in. In a related story, the Celtics allowed 38 second-quarter points against one of the worst offenses in the league thanks to numerous defensive breakdowns.

“We were small, and so when they were getting us on switches and getting us into the post we were overhelping – maybe not overhelping; we were recognizing the biggest threat and getting too sucked in and giving up the corner,” Stevens said of the defensive woes. “Especially at the end of the second quarter, you’ll see we had a small guy on the post and guys were trying to kick him out of there and as a result, they moved the ball quickly, they did a good job, they got open corner threes. It’s one of the reasons why we felt like we had to go big.”

The toughest thing for Stevens to manage at times this year is trying to find groups that remain solid together. When one issue is fixed, another one seems to pop up and that’s been the case with the defense by the starting five at times of late, which has sprung considerable leaks of late, thanks to sloppy rotations from the likes of Kyrie Irving, Jayson Tatum and Marcus Morris in stretches.

Playing Baynes more (he’s averaging a near career-low 14.3 minutes per game) also should help prevent the wear and tear on Horford at the center spot, who the team should be worrying about protecting more than ever give his injury situation and age. Horford has spoken repeatedly in the past about his preference of playing the power forward to BSJ and while he’s trying to be a good soldier for this group, the heavy onus of 70-plus games at the position risks him being at his peak for the postseason.

Baynes will become more of a bit player when the postseason rolls around but for now, he’s giving this team the best chance to win games on a nightly basis when he gets bigger minutes. The second half was a good start for Stevens but it can’t become a blip on the radar. Baynes needs to start playing 20-plus minutes each night, a move that will carry plenty of benefits for the short and long term with this group.

Consistency is a hard thing to find with this group this year, but one thing that Baynes is always good for is solid defense and energy. Amid an up-and-down season, it's time for more of that.