If you forgot about this play from last night, you would be forgiven. After all, it happened right after this: That oop by Rondo was such an impressive play that it got it’s own bullet point in our recap, and it was the lede in Jay’s excellent story over at MassLive. So the defensive stand immediately following might not have even registered as a blip on most people’s radars. That would be understandable.But the following defensive stand was noteworthy. Here’s the full video:At first glance, it just looks like DeMar DeRozan took a tough shot and missed it. But looking a little closer, we see that this is actually an example of two new Celtic players helping on defense, something that has been sorely looking in the first part of this season.It starts when Jonas Valanciunas screens Rondo off of DeRozan and rolls to the hoop, dragging Rondo with him like a riptide carrying away a small child. Sullinger hedged on the screen nicely, then sees Rondo getting stuck. This kind of awareness has been missing so far this season, as well as the trust Sullinger shows in his teammates’ help defense as he sticks with DeRozan, allowing other defenders behind him to pick up his man.But it’s not just Sullinger who sees this problem developing. Since DeRozan is faster than Sully, he’s able to create some extra space on his drive and pull-up. Jason Terry recognizes this immediately and helps off his man, Calderon, who DeRozan isn’t looking for because DeRozan frankly kind of sucks at passing. DeRozan shakes Terry with a pump-fake (and Sullinger starts to go for the fake as well), but in taking the extra time to use a pump-fake, DeRozan allows Sullinger to get back and contest the REAL shot, which he misses badly.But Sullinger isn’t done yet. After contesting the shot, he does what he does best: crashing the defensive boards, which turns out to be a good thing. DeRozan misses short, so had Sullinger not hustled down to grab the rebound, Valanciunas would have had ideal rebounding position for the board and the putback. Instead, Valanciunas crowds Sullinger too closely and picks up the foul bumping him out of bounds.This wasn’t a game-changing play necessarily, nor was it a highlight like the play that immediately preceded it. But it did show that Boston’s defense is starting to trust each other and work together as a unit, rather than as a group of individuals. This is incredibly important for a team with several aging centerpieces. More plays like this would be a huge step in the right direction for a team looking to resume their spot atop the defensive standings.Follow Tom on Twitter: @Tom_NBA.