Monday night's 118-113 loss to the Dallas Mavericks felt a lot like déjà vu for the Boston Celtics. Despite the exciting and downright exhausting second half comeback, the dismal first half effort was reminiscent of their February match-up.

Last season, the Mavericks tore apart the Celtics' pick-and-roll defense, getting whatever they wanted, scoring 54 of their 102 points via the pick-and-roll.

The first half of Monday's game was really no different, when 15 of Dallas' 26 makes were derived from the pick-and-roll. Boston trailed 67-41 at halftime, and the 26-point deficit was too much to overcome.

"You have to play. You can't start that way against anybody and you can't start that way against the best offense in the league," Brad Stevens told reporters after the game. "I don't want to make it like it's the comeback of all comebacks. It doesn't change the fact that you can't play like that [in the first half]."

Stevens didn't seem too keen on looking at the positives, as he inferred that Dallas just "let up," which allowed Boston to storm back and make a game of it.

While the Celtics' effort was admirable and is certainly something they can build on, Stevens is going to spend most of his time watching film, looking for ways to fix what went wrong in the first half.

The chart below details the Mavericks' first half offense, which looks at the play type in which each made basket was derived. For example, an "Isolation" score may have resulted in an assist, but the start of the play was an isolation.

Dallas' First Half Offense Play Type Makes % of Offense P&R Off-Ball 8 30.8% P&R Drive 2 7.7% P&R Pull Up 2 7.7% P&R Roll Man 1 3.8% P&R Pop 1 3.8% P&R Lob 1 3.8% Transition 4 15.4% Isolation 5 19.2% Post-Up 1 3.8% Dribble Hand Off 1 3.8% Total P&R Makes 15 57.7% Total Makes 26

It's clear that Boston's prominent issue was the help defense off of pick-and-rolls. Dallas was eating them alive with eight made baskets via off-ball looks.

Here is a compilation of all eight off-ball baskets:

Of those eight plays, Dallas had five three-pointers, two layups, and one dunk. That is exactly what you don't want a team to get out of the pick-and-roll, as mid-range jumpers or tightly-contested threes are the preferred result.

The Mavericks received these relatively open three-point attempts because the Celtics were overloading on the screener/roller, who was usually the problem last year, when Samuel Dalembert and Brandan Wright were dunking every other possession. Boston did well preventing lobs to the roll man, but the byproduct was open threes.

On this play, Kelly Olynyk shifts over to the "nail" (the middle of the free throw line) in order to slow down Tyson Chandler, one of the NBA's most devastating threats when he's rolling like a freight train down the lane. However, dropping off of Dirk Nowitzki left him absolutely wide-open for a three-pointer. Dirk drills it, as you'd expect.

Here, both Evan Turner drops to the nail as a means of slowing down Brandan Wright, and Marcus Thornton goes to the circle to provide extra rim protection. The problem is that this leaves both Chandler Parsons and Devin Harris open for threes. Thornton actually does a good job of closing out to make a strong contest, but Harris drained it.

Jeff Green makes the same exact mistake as Olynyk did in example one. He drops to the nail to help on Chandler, but that once again left Dirk open.

The Dallas Mavericks have one of the league's most lethal offenses, but the Boston Celtics need to play better fundamental team defense if they want to have a chance of beating contenders on a consistent basis, because desperation second half efforts and miracle comebacks aren't going to happen every night.

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