Tom Thibodeau held his end-of-the-season news conference Monday and the Timberwolves coach/basketball czar managed to smile when asked about his critics.

“My critics?” he replied with a sly grin.

He was being sarcastic. Thibs comes across as a coach who spends every second of his day fixated solely on basketball locked inside a bunker, but he surely knows that many people outside the organization are far from satisfied by a season that produced a 16-win improvement and long-awaited return to the playoffs. And that isn’t entirely fair.

The season was not a bust. The Wolves had a number of positive developments. The regular season should have been better — even with Jimmy Butler’s knee injury — but making the playoffs represents an important milepost for an organization searching for tangible signs of progress.

But how do they take that next step? Or that big leap, because that is what’s necessary — a sizable leap — before the Wolves can be considered legitimate championship contenders.

The answer is the same as always. Their defense — Thibodeau’s noted area of expertise — must become more credible.

“There’s times where we do play pretty good defense,” Thibodeau said.

Not consistently. Not from starters and bench. And certainly not enough to make them a postseason threat in the stacked Western Conference.

The organization pursued Thibodeau two years ago largely because the Wolves were terrible defensively and he had a reputation as one of the smartest defensive minds in the game.

The Wolves have shown growth on that end under Thibodeau, but not to the degree that was anticipated after adding Butler and Taj Gibson last summer.

The Wolves ranked 27th in defensive efficiency the season before Thibodeau’s arrival. They finished 26th last season and moved up to 22nd this season.

They finished 17th in points allowed per game this season, up from 23rd two seasons ago.

So an uptick has occurred, but the Wolves still rank in the bottom third of the NBA in defensive rating.

Of the 16 playoff teams, only the Cleveland Cavaliers finished lower than them in that category.

Six of the league’s top nine teams in defensive rating are still playing in the playoffs. So the blueprint isn’t a mystery.

“Obviously we’ve got to do better in that area, and the idea is to be in the top 10 in both [offense and defense],” Thibodeau said. “Obviously if you’re in the top five offensively, [the goal is] to move the needle defensively.”

Solving their dearth of three-point shooting should be a top priority too, but the Wolves still posted the fourth-ranked offense in the NBA despite ranking dead last in three-point attempts and makes.

Can the Wolves become a top 10 defensive team with this current roster construction?

Doubtful. More roster tweaks are necessary.

Both Karl-Anthony Towns and Andrew Wiggins showed improvement this season but they also had defensive lapses that were glaring. Commitment in that area can’t be occasional or when the mood strikes. It has to be consistent, a total buy-in.

They have enough experience now that youth shouldn’t be an excuse anymore. Butler’s head might explode if he’s forced to spend another season publicly complaining about a lack of effort on defense.

The roster needs more players who possess defensive aptitude, whether those players come via trades, free agency or draft. Thibodeau and GM Scott Layden face a challenging offseason in trying to strengthen the roster while attempting to sign Towns and Butler to extensions.

Thibodeau acknowledged that the Houston Rockets and Golden State Warriors have separated themselves from the pack in the Western Conference. The gap between those two and the rest of the field is daunting. The Wolves saw that gap firsthand in the first round, in both shooting and defense.

The Wolves had the lowest output in three-pointers in the NBA, so any improvement there should be substantial. But to become a legitimate contender requires more than subtle improvement on defense. They won’t take that next important step by simply being average on that end.