Back in the day, when the Chicago Bulls were a defensive menace, assistant coach Johnny Bach would draw an ace of spades on the bulletin board after big wins to signify a victim erased.

The U.S. Navy veteran used the military’s “card of death” as a metaphor for his team’s take-no-prisoners approach to defense, personified by Michael Jordan, Scottie Pippen and Horace Grant during the first Bulls threepeat from 1991-93.

Defense was always the Bulls’ calling card in their winning eras, since the days of Jerry Sloan and Bob Love — who died last week at 81 and was honored before Friday’s game against the Atlanta Hawks — to the Tom Thibodeau era.

It’s hard to imagine what Bach, a legendary coach under Phil Jackson, would think of the defensive shortcomings of this Bulls team, which entered Friday’s NBA Cup game at the United Center allowing 122.9 points per game, second worst in the NBA.

That’s 9.2 points more than last year’s average and an astonishing 31.1 points more than Thibodeau’s 2013-14 squad, which led the league in allowing 91.8 points per game.

It’s early, of course, but 16 games into the season the Bulls were on pace to erase the franchise record for highest opponents’ average, held by the 1966-67 team that allowed 116.9 points per game in the franchise’s inaugural season.

That was before the 3-point shot was introduced to the NBA, so it’s difficult to compare the teams. Naturally the NBA is much different now with more teams turning to analytics and shooting 3s without blinking.

The high scoring average against is also a byproduct of the Bulls’ faster-paced offense, which has led to a more entertaining game than some recent years. But the defense is a glaring problem, and the big question is whether they’re just going to have to live with opponents scoring 120 points or more or if the defensive issues are fixable.

“For sure (they are),” guard Ayo Dosunmu said before Friday’s game. “Just locking into some coverages, some small, minor details, I think that’s what’s holding us back from being the defensive team we want to be.

“It’s not too far off. Like I’ve said, we’re 6-10. We easily could be 8-8, or 9-7. But we’re here now and have a great opportunity this weekend, these two home games (against Atlanta and the Memphis Grizzlies). It’s just about moving forward.”

The Bulls’ latest defensive concern is the loss of Patrick Williams, who has a left foot injury and is sidelined for an undetermined length of time. Coach Billy Donovan said the MRI is only showing inflammation in the foot, and doctors haven’t said it would be a long-term situation.

“I don’t think the doctors were overly concerned that this was something abnormal,” Donovan said. “But any time a guy has surgery and he’s having some discomfort in there, you’d be naturally concerned. … Once it settles down and it gets back, does this reoccur? Is he totally fine? I don’t know. Nobody knows. I think it’s going to be how he responds.”

Williams said Friday that the last back-to-back games was when he first felt the pain, and the discomfort is not unexpected after last season’s surgery. Making it more frustrating is the fact he had been playing much better. He’s second on the Bulls with 15 steals and scored 17 points with a steal in Cleveland on Nov. 15, marking a career-high five straight games with double-digit scoring and at least one steal.

“I’m trying to find a way to say it nicely,” he said. “Obviously going through it and being out for so long, and you finally get a chance to get back and get some rhythm back, some touch and feel back, and when it happens, it’s frustrating to say the least. I’ve been through worse.

“I think this is a great opportunity for guys in the locker room to step up, and we’ve shown we can do that over history.”

Torrey Craig and rookie Matas Buzelis are among the bench players who will get those opportunities for a team looking to find itself after a rough start.

Dosunmu said the “vibes are good” in the locker room and feels the Bulls are mostly playing up to “their identity on both ends of the court.”

That’s debatable, particularly on the defensive end. Last week they gave up 144 points in a loss at Cleveland, and then 143 in a home loss to the Houston Rockets.

“There are some games we haven’t done that, like giving up 140 (points) back-to-back,” Dosunmu said. “But for the most part we’ve been trying to be cognizant of playing the right way and playing to our ability. That takes time. We’re staying with it.”

Dosumni pointed out a big group — eight teams — were within 1½ games of each other in the bunched-up Eastern Conference. They’re in the Nos. 5-11 spots. Only four teams were over .500 in the East, which suggested a mediocre Bulls team could still compete for the playoffs or at least a third straight play-in spot.

Then again, the Bulls need to improve just to qualify as being mediocre. Friday’s NBA Cup game on the bright red court at the United Center was a perfect chance to rebound from an awful defensive performance in Milwaukee.

Fans and media seemingly aren’t interested in the Cup matchups, which take place sporadically and over a month’s time. But Dosunmu said the players are very much into the in-season tournament.

“That’s $500,000,” he said of the winners’ share. “As a competitor you’ve always got that in the back of your mind. … Everybody in the top four gets money. You’re getting money to do it, getting paid on top of getting paid. That’s fun, and I think it brings more competition during the season, because the season is so long.”

There’s still plenty of time for the Bulls to turn things around defensively, but the clock is ticking.