The Cleveland Cavaliers were a terrible defensive unit this season. They allowed 109.5 points per 100 possessions during the regular season. Only the what-are-they-even Phoenix Suns were worse (110.6).

Personnel was an issue, though it got a little better after the roster swap at the trade deadline. There was no consistent scheme in place — at least not one that made sense. Effort, especially from LeBron James, was an issue throughout the year. The defense was as bad as ever, but many still waited for a “switch” to be flipped.

Narrator voice: The switch never flipped.

The Cavs posted a 107.4 defensive rating against the Pacers in round 1, a mark that would've ranked 18th in the regular season. That number rose to 110.1 against the Raptors in round 2, even though Toronto was somehow much worse.

The Boston Celtics were more than ready to take advantage of Cleveland's defensive shortcomings. Boston torched the Cavs in Game 1 on Sunday, boasting a 114 offensive rating and a 51/37/85 shooting split in a 108-83 win. Three Celtics — Jaylen Brown (23), Marcus Morris (21), and Al Horford (20) — scored 20 or more points, while Jayson Tatum chipped in with 16 of his own.

It didn't matter what the Cavaliers did, or what situations they were put in. Pick-and-rolls. Dribble-handoffs. Transition attacks. Half-court sets. They were flambéed. Botched switches, poorly-timed help (if any came at all), and shoddy effort doomed Cleveland from the opening tip.

No, literally:

Pick-and-roll breakdowns

Boston was able to waltz their way into good looks whenever they ran high pick-and-rolls. They forced big-on-small switches early and often. Any pick-and-roll involving Horford led to an open shot or a drive that scrambled Cleveland's defense. Marcus Smart was still treated like a scoring threat despite having plenty of time to scheme for him. It was a mess.

Here, a Rozier-Morris pick-and-roll forces a switch. George Hill is a good, long-armed defender, but he doesn't have the mass to keep Morris from the basket.

Smart and Morris go into their two-man dance and get a similar result.

Just look at the coverage. Hill prepares to go over the screen before Morris wipes him out. LeBron does nothing to pressure the entry pass. It couldn't be any easier for Boston.

One would think that the simple adjustment would be made — make Smart shoot. But … no. Not at all. This is the next offensive possession.

Not only is Hill getting ready to go over, look at how high LeBron is. It looks like Cleveland is preparing to trap MARCUS SMART instead of dropping and daring him to shoot. Smart uses Hill's momentum against him and goes away from the screen. Kevin Love steps up to contain the driving, leaving an opening for Smart to slip a dime to Aron Baynes.

Smart isn't done wrecking havoc in pick-and-roll. Here, he takes advantage of Cleveland's “drop” scheme by finding Horford on the pop.

It doesn't get much easier than that.

Poor (or no) help defense

The Cavaliers had enough trouble defending Boston's initial action. Their help rotations  were … also not great. Guys were late or inattentive. When faced with pick-your-poison decisions, Cleveland routinely chose the worst possible outcome.

Above, Cleveland decides to trap Tatum on the pick-and-roll to get the ball out of his hands. Tatum swings it to Smart as Cleveland tries to recover. LeBron, who initially drops to tag Baynes, hustles back to Semi Ojeleye in the corner. Rodney Hood then leaves Brown in the left corner to tag Baynes as Tristan Thompson tries to get back in the paint. Brown is left wide open for a triple.

This is where scouting comes in. There was no real reason for LeBron to leave Baynes. In a situation like that, you dare Ojeleye to beat you. Ojeleye shot 32 percent from three, and a little over 37 percent from the corners on very low volume. If he knocks it down, tip your cap. Don't force an extra scramble, especially one that involves Rodney Hood making bang-bang decisions. It won't end well.

On this play, Cleveland actually treats Ojeleye as a non-threat, but does so too late.

Just look at the hesitation from Kyle Korver to rotate over. He should leave the second he sees J.R Smith rotate over to Horford. It's also clear Love had no idea of what his assignment was after the pass was made. This is elementary stuff.

Also elementary: not helping from one pass away. Watch Jeff Green here.

This drive is contained. I understand that was something that couldn't be said for 85 percent of the game, but it's true! Green digs down for no real reason, leaving Morris wide open for an in-rhythm triple.

What is LeBron doing?

Oh, LeBron isn't getting out of this thing unscathed. The leave-Baynes-for-Ojeleye thing was questionable, but not indefensible. In general, that was his actual rotation — he's just smart enough to know when he should alter the gameplan.

There's no excusing stuff like this.

There is no effort given in transition here. Peep the beginning of the clip. Morris and LeBron are nearly level as the rebound is secured. As Morris turns on the jets, LeBron looks at him and goes into an “Ah, he's [Love] got him” trot. Horford pushes the break, creates a 2-on-1 situation and finds Morris for the bucket.

What you'll see below: Boston executing a fast break to near perfection.

What you won't see below: LeBron making any effort to get back into the play.

This is more of an optics thing. Complaining about a missed call during live action is never beneficial to your team. He probably doesn't get back in time to make anything happen (Andre Iguodala just shivered), but him making any sort of effort would've given Cleveland at least a slightly better chance at matching up instead of trying to account for a 5-on-4 on the fly.

LeThargic wasn't on his game on either end in Game 1. As the best player and leader of Cleveland, he has to do a better job of setting the tone moving forward. Now, we have a sizable sample size of him doing just that in Game 2s (and roughly 97 percent of his other games) so the panic meter shouldn't be up. But this was one of the worst all-around playoff games we've seen from him.

There should be some shooting regression on both sides in Game 2, but Cleveland still their work cut out for them. Their pick-and-roll coverage was flat-out disgraceful, and the rotations were sloppy or invisible. Those areas need to be sorted out and tightened up if they hope to steal Game 2.