The other day, I found myself writing, as one does, about Ersan Ilyasova. He is an elite charge-taker. What this means is that he’s elite at anticipating and positioning. He’s also probably a little quicker than someone his size has any right to be. These skills add up to make Ilyasova a really good team defender.

Recently, Zach Lowe had Zach LaVine on his podcast, and the conversation inevitably turned to defense. LaVine is a gifted athlete, but he does not (yet?) possess any of the attributes I listed above in describing Ersan Ilyasova. LaVine is actually a little less quick than you’d think he’d be, at least on the defensive end. He’s usually a step behind the action. He’s often in the wrong spot. Lowe asked LaVine if this is the kind of thing that a player can fix by just working harder, and LaVine talked about needing to trust his teammates more. The truth, I’m guessing, is that he isn’t sure.

Present day NBA basketball requires an incredible amount of strategy and communication on defense. Offenses are skilled at running their opponents through endless screens and ball-reversals, and defenders need to be able to switch assignments seamlessly while pulling one another out of bad matchups. Watch a good defense, and you’ll notice nearly constant talking and processing. Go play a pickup game sometime and you’ll immediately realize how exhausting this shit is. It wears you out.

Teams are so ready for switches and strategic ploys that they often let offenses dictate unfavorable terms. A team like the Rockets is so fundamentally ready to defend against mismatches that they often seem to invite them, baiting opposing big men into post-ups and out of more effective offensive sets. James Harden—ostensibly a guard—defends so many post-ups that he’s actually started to get more credit for his defense, even though his weaknesses on defense were the exact thing that caused the Rockets to defend the way they do.

Still, there must be a place for good, old-fashioned, on-ball defense, right? Last night, the Celtics totally flummoxed the Bucks in the 2nd half, turning a 19-point 1st half deficit into a big win. At the heart of this effort, beyond some hot shooting, was the defense of Semi Ojeleye, who over and over again simply stayed in front of Giannis Antetokounmpo. There was no real mystery to it. Just quick feet and good instincts. Semi seemed to be perfectly squared up on Giannis on every possession.

Those little moments bloomed into a big deal. Late in the game, the Bucks were frustrated. Their vaunted ball movement and their fast-paced drive-and-kick game were stuck in mud. Khris Middleton kept them in it with some incredible shot-making, but eventually that stuff ran out of steam.

How does one assess the value of a player like Semi Ojeleye, who, as Brian Scalabrine put it during the C’s telecast last night, has probably spent as much time thinking about guarding Giannis as anyone in the league (see: 2018 NBA Playoffs, Round 1)? I’m not sure, but I’m glad he’s on the team I root for. Sometimes, you just need guys who can stay in front of the great ones, because defense, finally, is just about being there a little early, profoundly in the way.