BOSTON — Since the start of the season, Kasparas Jakucionis has been more concept than reality for the Miami Heat. Last June’s first-round pick out of Illinois first dealt with a preseason groin strain, then worked his way back into shape in the G League.

But, arguably for the first time, there now is expressed confidence from the staff that the 19-year-old Lithuanian is ready for something more.

Jakucionis’ time could well be at hand — including a 7:38 cameo in Thursday night’s 106-95 victory over the Brooklyn Nets at the start of this three-game trip — as the Heat work through a series of injuries elsewhere on the roster,

“What I will say is he’s here for a reason right now and not in Sioux Falls,” coach Erik Spoelstra said, referencing the Heat’s G League affiliate. “I was extremely pleased with his eight games in Sioux Falls. Every game, he got in better game condition. He’s in superior shape, but also more confident. He did things that contributed to winning.

“Yes, because of where we are now with key guys out, he’s here on deck.”

Including pinch-hitting on Thursday night, which included his first NBA points, on a first-quarter 3-point at Barclays Center, his only shot of the night.

Spoelstra said Jakucionis showed enough in Sioux Falls to show he is ready for a next step.

“He makes things happen,” Spoelstra said, with the Heat moving on to Friday night’s game against the Boston Celtics at TD Garden. “You feel his presence right away. I’m really encouraged about him as a competitor. He does things to make you notice. He’s trying to impact the game in whatever minutes he has.”

Spoelstra then went into specifics.

“Great toughness and energy about him,” Spoelstra said. “He really competes defensively. And offensively, he just makes things happen. I like the progress he’s made.”

Over his eight appearances with the Skyforce, Jakucionis averaged 16.6 points, 5.8 rebounds, 5.6 assists and 2.3 steals, albeit while shooting .420 from the field and .326 on 3-pointers and averaging 3.1 turnovers.

And then came Thursday night. Until the Nets game, Jakucionis’ sum total of NBA experience was  54 seconds of mop-up duty in the Dec. 1 home rout of the Los Angeles Clippers.

This time, he was presented the game ball after the victory in Brooklyn.

“I had some little hints, just be ready like always,” Jakucionis said of getting Thursday’s call. “I’m trying to be ready always and do what I can do, control what I can control.

“And every time I have a chance, I’m trying to use it.”

Spoelstra said Thursday, although a baby step, was a step forward.

“I thought he gave us a good boost,” he said. “We’re down guys right now. Kas gives us the energy, the competitiveness. He makes things happen. He’s gotten a lot better, a lot more comfortable in what we’re trying to do. I thought those minutes were good.”

Jackucionis said the time with Sioux Falls was beneficial, both from rehab and growth standpoints.

“I think it’s just going step  by step,” he said, with the Heat’s three-game trip concluding Sunday night against the New York Knicks at Madison Square Garden. “The eight games in Sioux Falls really helped to I think get in rhythm. You’re playing, doing what you need to do. And I think day by day, you feel more and more comfortable.

“And I’m trying to prove — even if it’s like 1% every day, I’m trying to get better. So I think that leads to confidence to get more comfortable on the court and just do better.”

Like Spoelstra, Jakucionis was asked about where his growth has come over these past two months largely out of view.

“I think overall kind of everything, to be honest,” he said, “because I was a little bit out of rhythm after the injuries. So I just got in rhythm, tried to play faster, tried to push the ball more, find my open teammates, focus on the defensive end.”

That pace led to the pros and cons of his Skyforce experience, but was also critical in being able to mesh with the Heat’s up-tempo approach.

Spoelstra said the most important element of Jakucionis’ G League stint was consistent reps, no matter the numbers.

“The most important thing right now is he just needs to play. It’s not even necessarily about evaluating him right now,” Spoelstra said. “He had some good weeks during the summer, and then it was just unfortunate the injury. He even asked me, ‘What did I need to work on?’ I said, ‘Don’t stress out about that right now. It’s about getting out there and playing. And then we’ll take that next step when it comes.’ ”

Now, that next step potentially stands to be at hand.

Said Spoelstra, “He’s significantly improved from where he was in the summer.”