The Milwaukee Bucks defense had a great start to the year. Unfortunately, Brad Stevens unraveled them on Thursday night.

The Milwaukee Bucks were on the wrong side of history on Thursday night against the Boston Celtics. Boston set a franchise record with 24 made threes on the night and just barely missed out on tying the NBA record which sits at 25.

The Bucks defense was bleeding three-point attempts all game long as Boston hoisted 55 of them. It appeared to be Bucks’ head coach Mike Budenholzer’s strategy coming into the night and it’s easy to see why. Before Boston’s barrage of threes, they ranked 24th in the NBA in three-point percentage at 32.8 percent. So it makes sense why Budenholzer created his game plan around allowing the Celtics to shoot three after three after three.

At the end of the day, Budenholzer didn’t do anything different than what he had drawn up for his defense in the first seven games of the season. The defensive lapses came down to two issues; overhelping and playing drop coverage in the pick-and-roll:

In the following clip, Kyrie Irving disrupts the Bucks’ whole defense with his dribble penetration into the middle of the lane. This forces Brook Lopez to slide into the middle (for no reason really) and deter the drive, leaving Al Horford open for a wide-open three:

Following a dribble-handoff from Gordon Hayward, Irving is able to get an advantage on his man and drives toward the middle of the lane. Even though Giannis Antetokounmpo is in a great help position, Lopez also drops into the paint to stop the drive. Irving then kicks it out to Horford at the top of the key for an easy trey.

Although it’s hard to be fully aware of Budenholzer’s principles, typically a player isn’t supposed to help on a drive when they are only one pass away. This puts that help defender in a tough position as we saw there with Lopez.

Here’s another example except with Khris Middleton playing the role of the culprit:

Hayward begins by receiving a ball-screen from Aron Baynes and Lopez is implementing drop coverage. Drop coverage means the big man sinks into the lane on the ball-screen and is responsible for preventing the ball-handler from getting to the rim.

With Lopez backpedaling as Hayward attacks, Middleton, who’s guarding Semi Ojeley on the weakside wing, feels compelled to step up and stop the drive Lopez is responsible for. This leaves Ojeley open for a catch-and-shoot three.

Even though Ojeley is a career 31.8 percent shooter from downtown, there’s still no reason for Middleton to step up in that situation. Lopez already has the drive under control and is more than capable of handling a healing Hayward in the paint.

This next play starts halfway through the action, but it’s already clear Tony Snell has a good handle on Marcus Morris driving to the rim. He’s got his shoulders squared and does a very good job of staying in front of him and then staying disciplined on the shot fakes:

But once again, a Bucks’ defender feels the necessity to get deep into the lane to help out his teammate who clearly has things handled. This is the case with Ersan Ilyasova as he’s sitting deep into the paint on this play. There’s absolutely no reason for Ilyasova to be that deep.

Even with the Bucks propensity of overhelping, that still wasn’t their biggest issue against the Celtics. The drop-coverage they implemented in the pick-and-roll allowed Boston to knock down the threes in waves like they did.

The following video highlights all of the issues with the Bucks pick-and-roll defense last night and exactly how the Celtics were able to take advantage of it:

In addition to the drop coverage, the Bucks defense also left them vulnerable to schematic changes by Stevens. Budenholzer shouldn’t beat himself up too bad when it comes to this department, however, as Stevens is the best coach in the game for a reason:

The play begins with Horford signaling to Terry Rozier as if he’s going to set a ball screen. Once Ilyasova believes Horford is setting the pick, he begins to drop into the lane. As Rozier dribbles to the wing he looks back to see Horford setting an off-ball screen on Bledsoe in order to get Irving a wide open look from the top of the key.

Of course, it helps that Bledsoe loses focus and allows Irving to get so wide open. However, the main idea behind this action is that because of the ball screen, Ilyasova is way out of position to help on the next pick and it gives a good shooter a nice, uncontested look.

Budenholzer has stuck with this defense throughout the first seven games of the season and largely did so against Boston. It wasn’t until the final two minutes where he began to switch on defense. And, uncoincidentally, the Bucks forced a long contested two when they did so:

Before the video starts, Ilyasova had switched onto Gordon following a ball screen. The rest of the Celtics then clear out to allow Hayward to go one-on-one with his new defender. However, Ilyasova does a nice job of moving his feet and forcing Hayward into a contested 20-footer. Exactly what Budenholzer wants.

Here again, the Bucks implement something other than drop coverage:

As Horford is setting the pick, you’ll notice Ilyasova is a lot closer to the three-point line this time around. Instead of sitting back around the free throw line, he’s just a couple of feet inside the arc. It doesn’t necessarily look like the Bucks are switching this, but just by being closer to the ball-handler, Ilyasova is able to contest Irving’s three and force a miss.

Without a doubt, Budenholzer knows Boston just gave the rest of the NBA a blueprint on how to attack their defense. However, the key area to watch will be how Budenholzer adjusts to those adjustments.

Depending on the personnel the Bucks have on the floor, there are a couple of different options they can go with. Unfortunately, given the limitations of some of their big men (Lopez), they won’t always be able to implement a defense that switches or one where the big man hedges on ball screens. Regardless, there are a plethora of options Budenholzer has at his disposal. We just have to have faith, this isn’t Jason Kidd after all.