The Wizards are allowing opponents to shoot more effectively both close to the basket and on three-pointers. (Alex Brandon/Associated Press)

When the Washington Wizards decided to carry over the smaller, faster style they implemented last postseason to the 2015-16 campaign, they recognized the top challenge was sustaining the elite defense that ranked among the league’s best each of the past three seasons.

“That’s where we can’t take a step back,” Wizards Coach Randy Wittman said after the Wizards’ preseason debut on Oct. 6. “Are we going to stay committed to being that dirty, dirty team defensively? Those are the things I’m going to have to hold them accountable to.”

More than a quarter of the way into the regular season, the Wizards aren’t close to resembling that squad. Through 24 games, they rank 27th in the NBA in points allowed (106 per game), 25th in defensive efficiency (105.1 points allowed per 100 possessions), and tied for 28th in opponent’s field goal percentage (46.9).

They ranked in the top seven in each of those categories last season. Consequently, they’re 10-14 and sitting in 12th place in an improved Eastern Conference, miles from the pace they envisioned.

Coach Randy Wittman’s Wizards own the league’s worst three-point shooting defense. (Jonathan Newton/The Washington Post)

“We’re not a team that’s going to be able to outscore people,” point guard John Wall said, “and that’s what we’re trying to do right now.”

Wizards brass conceded before the season that the adjustment would take some time, but the team was confident its benefits would mitigate growing pains. So far, that hasn’t happened. The pace-and-space offense led by Wall generates more scoring opportunities but also more turnovers, failing to offset the drop-off on defense. The Wizards’ deviation from two traditional big men has not had the intended effect of better countering the perimeter-oriented strategy most of the league adopted before them. And a roster that was mildly tweaked from a defensive perspective — the only players to log significant minutes last season who didn’t return, Paul Pierce and Kevin Seraphin, weren’t strong defenders — has not coalesced.

The results are grisly: Perhaps because of its smaller front court, Washington has allowed opponents to shoot 61 percent from within five feet of the basket, fourth worst in the NBA. But in a head-scratching development for a team that regularly puts four perimeter players on the floor, the Wizards own the league’s worst three-point defense, allowing 40.9 percent shooting from behind the arc on 25.3 attempts per game. No team in NBA history has allowed opponents to shoot that high of a percentage on at least 25 tries over an entire season.

The team has repeatedly refused to use injuries as an excuse, but the reality is key pieces are missing. Nene, moved in the offseason to backup center despite being considered the team’s best interior defender, has missed the last 11 games with a strained calf muscle. Guard Bradley Beal, who has made strides as a perimeter defender, is expected to sit out at least the rest of the month with a fibula injury. Swingman Alan Anderson, who was signed during the summer for his defensive ability, hasn’t played yet after undergoing ankle surgery in October.

Ask Wittman and the players, and the consensus is that neither scheme nor personnel are the problems. In their view, the frustrating plunge derives from three essential tenets: effort, communication, and mental preparation.

“The bad thing, that I thought this team would be better at, is [avoiding] the mental mistakes,” forward Jared Dudley, who was acquired over the offseason, said after Monday’s loss to the Memphis Grizzlies. “When we have a game plan, follow the game plan. The one time we had a game plan and they just beat it was [against] Indiana. . . . Besides that, guys are getting wide-open looks. And that’s because of the mental preparation of how we’re supposed to do the coverages. One guy has an error here, another as an error there. And that’s what we have to clean up. The only way we can do it is watching film, calling teammates out, try to do that. And we’re trying to.”

“We’re not a team that’s going to be able to outscore people,” point guard John Wall said, “and that’s what we’re trying to do right now.” (Alex Brandon/AP)

Most of the Wizards’ defensive lapses are induced by basic dribble penetration or having to double-team in the post because of their thin front court. Both situations force them to scramble to rotate. Sometimes they don’t aggressively close out on a good three-point shooter, leaving him open. Sometimes they aggressively close out on a bad three-point shooter, leaving a more effective option open. Sometimes two defenders collapse on one player and a player is left alone behind the arc or near the basket. Often, the other team scores.

“I just think in camp we focused on offense and our defense fell behind,” Wall said. “There are situations where the coverages we have are great. When we get our intensity into it, it helps.”

Guard Garrett Temple explained that the Wizards specifically have trouble once offenses improvise. When the Wizards recognize the play the opponent is running, they defend it well. When choreographed sets are tossed aside, chaos and points follow.

“When the play breaks down and we’re just playing basketball, it might be a random pick and roll or a random cross screen or a random cut backdoor, we’re not talking enough, we’re not communicating enough, we’re not aware enough,” Temple said. “And those are basic principles of defense: Communicate, see man and ball.”

What was recently so basic is now complicated for the Wizards, and the time to figure it out is ticking away.