Game 1 video breakdown: Tightening Theis' defense

Daniel Theis is in a tough spot. He knows he's going to be tested over and over again while the Celtics wait for Robert Williams to get back from his meniscus surgery. 

Part of the beauty of having Theis is that he can slide into Williams' spot without pulling too many other pieces out of their normal responsibilities. On offense, he can catch lobs and dump-offs while running some pick and roll and dribble hand-offs. Defensively, he's capable of helping and blocking shots, but he's just not able to make some of the spectacular plays Williams makes. 

The latter is one of two issues with Theis. The other issue is that while he's played with these teammates before in Boston, he hasn't done it as part of Ime Udoka's system. There are still moments where he's making the wrong decisions. 

For example, early in Game 1, Al Horford had done a great job switching onto Kyrie Irving and then Seth Curry, but when Theis came over to help at the very end, he was chastised by Horford for doing so. 

Horford has a great point here because he's been shadowing Curry the whole way and is prepared to challenge the shot. Theis' decision gave Curry a bail-out, which resulted in easy points for Andre Drummond.

That's something the Celtics are going to have to clean up in a film session. Recognizing when to help and when not to is critical in the playoffs because making the wrong call can lead to those easy layup and points the Celtics can't afford to give up. 

The other big issue with Theis in Game 1 was switching onto smaller players, particularly Irving. Boston employed a "drop" coverage where Theis dropped back on pick and rolls and he was summarily torched. The goal was to protect the rim, but instead Irving was able to score 11 points while being guarded by Theis. 

Here's how those plays looked.

What you didn't see was the three free throws Irving got for a landing-spot foul. That was an undisciplined closeout by Theis who took one added little step at the end of the play to get just far enough underneath Irving to commit that foul. 

Irving not only scored nearly a third of his points against Theis, but it was this kind of defense that lit Irving's fuse for the rest of the night. 

Theis' first attempt on the Irving/Nic Claxton pick and roll was bad: 

Irving missed that shot. But it got worse on the next attempt.

Marcus Smart lit into Theis from the bench after that play. Irving hit that shot and he kept rolling from there. 

Ime Udoka might be using the drop coverage to entice those mid-range shots from Irving, but they still need to be challenged to some degree. Theis coming all the way up to touch is probably too much, but he needs to be much higher here to at least make Irving think he has a path to the lane. 

The Celtics want Irving dribbling as much as possible. He does love to dribble the air out of the ball a bit, but there has to be a happy medium. 

This really seemed to be Udoka using his Williams game plan with Theis thrown in there. With Williams in there, the distance between him and Irving (or whichever ball handler aside from probably Kevin Durant) feels smaller because opponents know he can get way up off the floor and cover a lot of space in a hurry.

Opponents are emboldened against Theis because he simply can't come flying in out of nowhere like Williams does. So not only is Theis being asked to guard guards sometimes, he's being asked to guard guards who are less afraid of him and are more aggressive. 

Boston will have to adjust this coverage in Game 2. They are either going to have to send Theis higher to be more of a threat and be mindful of the rotations behind him or they're going to have to scrap the drop coverage completely and deal with the switching. Whenever Williams does return, they can go back to the original plan and see if that will work better with his athleticism.