SAN DIEGO — If the prevailing theme of Christian Braun’s offseason was trying to do more, he came up short in one category.

Sporting a mild stubble Monday morning inside Ball Arena, Braun proclaimed that he sprouted a beard during his time off and wanted to rock it at media day. Three days later, discouraged by negative reviews at training camp, he reflected on the journey.

“I was back home, and the full beard grew on my face. I didn’t really expect it,” Braun told The Denver Post, sitting behind the baseline of U.C. San Diego’s practice courts. “Some people like it. Some people hate it. Most people hate it. … The players aren’t fans of it. Some tell me to cut that (bleep) off.”

Braun was incredulous at the obvious follow-up question: So it was actually a full beard at first, earlier this summer?

“Why do you say ‘at first?’” the 22-year-old guard retorted. “It’s not a full beard now?”

The beard schtick, and Braun’s general use of humor-as-artifice recently when asked about his summer, has been his way of deflecting from the reality that this offseason was a crucial one in his growth as a rising NBA sophomore.

Same goes for Braun’s superstitious stance on the Nuggets’ first championship in franchise history. He attributes it to the “Frozen” backpack he was required to wear on road trips throughout his rookie season.

“Carried it every game, and we ended up being the 1 seed,” Braun told The Post. “… I’m not going to take it off if we’re having success”

Behind those jests is a player who has been intensely driven in his individual training, hellbent on earning an increased role in the Nuggets’ offense. Braun gave himself a week after the championship parade to rest before he started training with old friends in Kansas City. He didn’t even know for certain yet that the Nuggets would soon have more minutes to give out. In Braun’s mind, it was necessary to prepare as though he would take on a bigger role whether Bruce Brown remained on the roster or not. “My job isn’t to worry about who’s here and who’s not,” as he put it. “My job is just to prove myself.”

“He was the best player in our gym most days this summer,” Nuggets coach Michael Malone said. “And you’re just watching that confidence and that swagger he has, and the experience he went through last season in the playoffs, in the Finals. Not many rookies have the impact that he did.”

By the time Brown did sign a two-year, $45 million deal with the Pacers on July 6, Braun was entrenched in routine pick-up games in Kansas City partially designed to solve his steepest rookie obstacle.

“Reaction time, decision-making time,” Braun said. “Probably the biggest difference (from college to the NBA). People always say the speed, and I guess that’s sort of the same thing. But your decision-making time really cuts down. And whether you’re going to throw a lob, whether you’re going to go finish yourself, you can’t hesitate in the NBA. Or that gap’s closing because of the athleticism.”

Even for someone who exudes tenacity when he defends — Braun’s popularity with the fanbase was clear during the NBA Finals whenever he threw himself after loose balls — confidence could occasionally be a crutch for Braun as he tried to find his fit in an NBA offense, he admitted.

In the playoffs, he amassed a ratio of 11 assists to 10 turnovers while averaging 13 minutes. The previous year as a more prominent part of Kansas’ championship-winning offense, he had 22 assists and eight turnovers in the NCAA Tournament.

“There’s definitely a hesitation,” Braun said. “I think that’s natural. You come into the league, you hesitate a little bit. … There’s definitely still a learning curve.”

The only way to simulate that pace-of-play adjustment during an offseason?

“Play pick-up,” Braun said. “You play pick-up and make sure you’re playing high-level games, and you know you’re not wasting your time with anything. There’s no way to really replicate an NBA-level game. You’ve just gotta play in it, and that takes time. That’s why I really appreciate what Coach (Malone) and Calvin (Booth) have done for me, allowing me the opportunity to get these reps in my first year.”

Braun played religiously in Kansas City, then played three times a week with his Nuggets teammates after he returned to Denver around Aug. 10. He set a 3-point shooting goal of 40% for this season. (“My freshman year at KU on low attempts, I shot 44%,” Braun pointed out to The Post. “It was never a problem of ‘could I shoot,’ or a mechanical thing.”) He emphasized his transition decision-making in those runs.

“When you’re talking about apples-to-apples replacement (of Brown), you’re talking about Christian Braun,” Nuggets general manager Calvin Booth said. “And Christian, I think, has improved his ball-handling a ton, but he won’t be playing any backup point guard. … Christian Braun is going to bring a lot of the same things Bruce brought, but Bruce played on the ball more.”

From a usage standpoint, Braun figures to line up with the Brown minutes the Nuggets lost, even if their roles don’t precisely correspond. It’s a fitting setup for a replacement whose name is a homophone of the player he’s replacing.

Malone has emphasized at training camp that he doesn’t want Braun to change his game just because of a player who’s no longer on the team. Still, Braun wants to be prepared enough to do more, if the ball does end up in his hands at anywhere close to a Bruce Brown frequency. Malone says that with the right lineup, there could be scenarios when Braun does initiate the offense even though he’s not a true point guard.

“When I’m back home, just guys from Kansas City, I’m allowed to play with the ball in my hands a lot. I get to expand on my game in that way,” Braun said. “So that’s actually important to me. I get to go home and play against those guys and have the ball in my hands, and then I get to come here, and they still, all summer, allowed me to have the ball in my hands and allowed me to play in a different way than I played last year.”

Braun doesn’t actually think the “Frozen” backpack is the key to Denver’s title, obviously. He’s too experienced at winning championships to earnestly label anything a good luck charm, especially since that would discredit hard work. It’s all in good fun.

But he does wonder what Elsa’s fate will be this season. The backpack, acquired by Kentavious Caldwell-Pope early last season for Braun to carry around on road trips, is still sitting in Braun’s apartment.

The rookie was responsible for the grunt work. He kept a couple decks of cards available at all times, just in case players wanted to use them during a flight. If a deck got old or messed up, Braun diligently replaced it with a new one. He had phone chargers at the ready, too. All in the pink cartoon luggage.

“My rookie duty was to carry the ‘Frozen’ backpack,” Braun said. “I did my duties with a smile on my face.”

He could keep it this year, if it’s actually that lucky in his possession, but he might feel ready to move on.