CLEVELAND — Is the Cleveland Cavaliers’ defense good now?

That may be the most important question heading into The Finals.

The NBA started counting turnovers in 1977. Since then, no team had reached The Finals after ranking as low as 20th in defensive efficiency in the regular season … until now.

Ranking anywhere outside the top 10 in defensive efficiency is not a good sign for your hopes of winning a championship. Only three teams — the ’01 Lakers (19th), the ’95 Rockets (12th) and ’88 Lakers (11th) – have won the title after ranking outside the top 10 in the last 37 years. And all three had won the championship (with a top-10 defense) the year before.

Of course, if you’ve been paying attention, you know that the Cavs were a different team after they made some trades and got LeBron James back from his two-week hiatus in mid-January. Iman Shumpert had a shoulder injury when he arrived from New York and played his first game as a Cav on Jan. 23. And yeah, there was clear improvement from that point on.

With the personnel changes came some alterations to the Cavs’ defensive scheme. Early in the season, they brought their bigs out high to defend pick-and-rolls…

They changed things up by having Timofey Mozgov hang back at the free-throw line to better protect the rim and reduce the number of 4-on-3, scramble situations that his teammates got caught in…

But even if you pretend that the season started on Jan. 23, the Cavs still didn’t have a top-10 defense. Furthermore, their DefRtg was somewhat skewed by a relatively soft schedule. Against the league’s best offenses, they weren’t so good.

March 6, their last regular-season meeting against the Atlanta Hawks, was a good measuring stick for the improved Cavs’ D. And it got chewed apart by the East’s No. 1 seed, which scored 106 points on about 93 possessions. Six days later, in the game that Kyrie Irving scored 57 points, the Spurs scored 125 in what wasn’t a very fast-paced game either.

So the Cavs entered the postseason with some lingering (and serious) questions about their defense, which was, no matter how you looked at it, worse than the (11th-ranked) Miami Heat defense that got eviscerated by the Spurs in last year’s Finals.

Have the Cavs answered those questions?

They’ve held each of their three playoff opponents well under their regular season mark for offensive efficiency. And in that regard, they’ve been better than the Warriors, who had the No. 1 ranked defense in the regular season.

The Cavs’ defense is definitely improved. Though they’re not a defending champ like the ’01 Lakers, they seemingly knew how to flip the switch once the playoffs began.

There’s been more of a focus on that end of the floor. Multiple efforts from possession to possession have been more common. Losing Kevin Love less than four games into the postseason certainly helped the Cleveland defense, as Tristan Thompson is more active (to put it nicely). Extended minutes for Matthew Dellavedova (with Kyrie Irving hobbled) have helped as well.

The result has been more possessions like this one and this one. The Cavs have allowed less than 91 points per 100 possessions in 215 playoff minutes with James, Mozgov and Shumpert on the floor together.

But just how improved the Cleveland defense is may be more about context than it is about the raw numbers. The Chicago Bulls and Atlanta Hawks each had top-10 offenses in the regular season, but it’s hard to say that either were playing anything close to their best basketball when they faced the Cavs.

The Cleveland defense is the only one in the playoffs to have held its opponents under 30 percent from 3-point range or to an effective field goal percentage under 40 percent from outside the paint. While the Cavs’ rim protection has been OK, the numbers point to the perimeter as the biggest reason for them allowing less than a point per possession over 14 games.

But according to SportVU, the Cavs have contested just 29.7 percent of their opponents’ jump shots in the playoffs, a rate which ranks 11th out of 16 teams. Furthermore, the average distance for the closest Cleveland defender on opponent shots in the playoffs is 4.25 feet, a rate which ranks ninth.

Those numbers support the theory that the Cavs faced some good teams that were playing poorly at the time. The Hawks were held well under their regular season offensive efficiency mark in the first round by the Brooklyn Nets, who ranked 24th defensively. Atlanta shot 27 percent on uncontested jumpers in the conference finals, down from 41 percent in the regular season.

So we may not know just how good the Cavs’ defense has become … until Thursday. No team takes advantage of open looks better than the Golden State Warriors, who led the regular season with effective field goal percentage of 54.7 percent on uncontested jumpers, and have led the playoffs with the same exact mark.

The Cavs did hold Golden State under a point per possession in their Feb. 26 win in Cleveland. After starting 3-for-4, Stephen Curry made just two of his last 13 shots. Shumpert seemed to do a solid job on the MVP, who got just six touches and took just two shots in 2:24 of matchup time with Shumpert, according to SportVU.

Putting Shumpert on Curry means putting Irving on somebody else (who could punish him in the low post). It will be a puzzle for Cavs coach David Blatt to deal with throughout The Finals.

The Cavs have made a little history to get here. Now we find out if we can really forget those regular season numbers that told us they would come up short in the playoffs.