The Orlando Magic signed Bismack Biyombo for rim protection. He ended up more a liability than an asset in his first year with the team. But early this season, he has found his old self again.

After signing Bismack Biyombo, last year’s Orlando Magic were expected to be strong defensively if nothing else. But for whatever reason, he seemed a step slow all season. It was easier for opponents to back him down or get around him, both on the block and in space. And he did not make the same athletic plays he did with the Toronto Raptors.

Twenty-one games into the season, he is having a resurgence, making a compelling case to be inserted into the starting lineup. He is blocking more shots, defending guards on switches and holding his own in the post. He looks better athletically, and he has also benefited from having better wing defenders behind him.

Biyombo received a meager seven minutes Monday night against the Indiana Pacers. But in that short amount of time, he was a +2 and gave yet another glimpse of what this team’s starting unit has been missing. Namely, in a game where the Magic defense struggled overall, the Magic posted a defensive rating better than 90 with Biyombo on the floor.

It was because of plays like the one near the end of the first quarter.

Victor Oladipo ran a pick and roll with Myles Turner. Biyombo switched onto Oladipo, denied him a shot opportunity then recovered from out of bounds to emphatically deny Turner at the rim. It was one of his most impressive plays of the year and a play no one else on the roster could have made.

Defensive statistics are notoriously unreliable and noisy, but when evaluating rim protection, there are a few numbers generally accepted as strong indicators: block rate, opponent field goal percentage at the rim, and frequency of opponent shots at the rim. But these need to be balanced with the eye test.

Block rate measures the percentage of opponent two-point shots a player blocks when he is on the floor, adjusting for minutes and pace in a way that blocks per game does not.

Opponent field goal percentage at the rim evaluates a player’s ability to affect shot attempts that he does not block – since the majority of any player’s defended field goal attempts are not blocks, how do those attempts look? Do opponents finish with ease, or do they struggle to create an efficient shot?

Frequency of opponent shots at the rim, perhaps the most important of the three, indicates his deterrence factor: does he make opponents disinclined to even attempt what is usually the most efficient shot on the court?

Reducing opponent shot attempts at the rim comes partly from a player’s reputation (an offensive player may be less inclined to drive to the rack if he knows Rudy Gobert will be there). But it also has to do with positioning. Sometimes the better defensive play is not blocking a shot, but using either verticality or lateral mobility to get in position to deter a shot. The only thing better for a defense than an emphatic rejection is denying the shot opportunity in the first place.

Biyombo is starting to measure up in these three defensive metrics.

With Bismack Biyombo on the court, the Magic’s opponents shoot within three feet of the basket only 24 percent of the time, per NBAwowy.com. That is around eight percentage points better than it is with him off, and it would comfortably lead the NBA.

His current block rate of 6.5 percent would be a career high. If he qualified for the NBA’s leaderboard, it would be tied with perennial Defensive Player of the Year candidate Rudy Gobert for third place.

In a limited sample, he has also improved his efficiency defending post-ups from 0.87 points per opponent possession to 0.67.

Opponents have shot 59.8 percent in the restricted area against Biyombo. That figure is slightly worse than it was last year, but is still solid and stands between Joel Embiid’s 60.1 percent and Gobert’s 59.6 percent.

His blocks per game are up by 0.3 per game despite receiving six fewer minutes per game. His 3.0 blocks per 36 minutes, almost double last year’s rate, also would be a career high.

So, why is he so much better? What has changed?