Mike Bibby has made Heat’s defense much worse

In Atlanta, there are a lot of Hawks fans nodding their heads.

The Miami Heat’s defense is much worse when Mike Bibby is on the floor.

Not just worse, much worse. Tom Haberstroh crunched the numbers for the Heat Index at ESPN.

When point guard Mike Bibby has been on the floor for the Heat, Miami’s defense has surrendered 15 points per 100 possessions more than when he has sat on the bench. (We use per 100 possessions as the standard to control for potential tempo effects).

That sounds bad, but how damaging is that? Consider this: the difference between the league’s top defense (Chicago) and the league’s worst defense (Cleveland) is 12.5 points per 100 possessions. Do the math, and you find that Bibby’s defensive impact has been about three points wider than that.

With LeBron James and Dwyane Wade, the Heat have a couple of athletic and impressive perimeter defenders who can pressure the ball and get to help positions quickly. Few perimeter players can block shots like them. But that’s not how you hide a bad defender on the perimeter, you need a big man who can erase mistakes inside to pull that off well. The Lakers Derek Fisher is not a good defender but their length inside and shot blocking cover his mistakes. The Heat have Joel Anthony but he is not used regularly.

The Heat have had a good defense — fifth best in the NBA this season at 100.4 points per possession. They play a very different defensive style than the Celtics, but it works for them. From the first day Erik Spoelstra made defense the identity of this team.

But Bibby changes that.

But on defense? That’s where things get ugly. For much of the season, the Heat battled the Bulls and the Celtics for the league’s best defense. Now, the Heat have slid in the ranks down to fifth place, separating themselves from the cream of the crop. What’s most interesting is when that slide started: when Bibby came into town. He made his debut Mar. 13 against the Magic when the Heat allowed 99 points on just 89 possessions, translating to a defensive efficiency far above the Heat norm. The next game? The San Antonio Spurs dropped 125 points on the Heat.

So here are the numbers with Bibby in tow. Since that Orlando game (Bibby’s debut), the Heat’s defensive efficiency (points allowed per 100 possessions) has ranked 20th in the league at 106.4, according to data from NBA StatsCube. That’s worse than Cleveland, Minnesota and Sacramento over that stretch. Before that game, the Heat’s defensive efficiency stood at 99.7, one of the very best in the league.

There is what statisticians call “noise” in the numbers, something that Haberstroh admits (for example, Bibby came in when the Heat played their string of playoff bound teams, for one). Also, Bibby’s three-point shooting has boosted the offense when he is on the floor so despite how bad the defense is the Heat still tend to slightly outscore their opponents.

But Mario Chalmers does not have this kind of defense impact. Neither did Carlos Arroyo, the man the Heat sent out to make room for Bibby.

Right now, Bibby’s offense covers the problems. But in a playoff series where teams will work to isolate and exploit him, and to take away his offensive threes, Bibby likely will become a bigger issue for Miami.

Just ask the people in Atlanta.