BOSTON — An apology resurrected one season. A shift to the starting lineup revived another.

Along the way, his faith has been tested, his mood has fluctuated, his production has wavered.

But Portland Trail Blazers forward Moe Harkless hasn’t quite been through a season like this one, when the one thing he’s almost always been able to count on — his health — has sapped his confidence and thwarted his talent.

“It’s been a tough year, dating back to last year when I got hurt,” Harkless said. “It’s been a battle. It’s been up-and-down. It’s been frustrating at times. But I just stuck with it, I’m continuing to stick with it, and it just feels good to be playing and playing well.”

As the Blazers added yet another impressive victory to yet another post-All-Star break surge, beating the Boston Celtics 97-92 Wednesday night at TD Garden, Harkless continued a little surge of his own. The Blazers’ starting small forward finished with a season-high 17 points, a season-high 10 rebounds and three steals, while making 8 of 13 shots. It was his first double-double of the season and the fourth time in the last five games he’s reached double-figures in scoring.

The Blazers (38-23) earned their fifth consecutive victory — their longest winning streak this season — and Harkless was everywhere, snatching steals, harassing defenders, deflecting passes, corralling offensive rebounds, driving to the hoop for dunks and generally wreaking havoc on the Celtics. And perhaps the most important part of it all, the part that could mean the most for the Blazers over the final 21 games of the season, was that the performance wasn’t a one-hit wonder.

As the Blazers have opened a seven-game East Coast trip with four victories, Harkless has flourished, averaging 13.0 points, 7.8 rebounds, 2.3 assists and 2.0 steals, while shooting 56 percent from the field. It’s his best stretch of the season and it’s not even close.

“I’m just in a better place physically and mentally,” he said. “I feel good, so I’m not thinking about anything. I’m just out there playing, and that’s when I play my best.”

Harkless, of course, has not been at his best all season as he’s endured lingering pain in his left knee, a byproduct of arthroscopic surgery last March. He’s missed 20 games and even when he has played, he rarely has looked — or felt — quite right. He doesn’t always know how his knee will feel when he wakes up in the morning, let alone how it will feel during games, when a sharp cut here or a random pivot there will send an uncomfortable surge to his knee.

And while there have been points during the season when he said he thought he was turning the corner, when he truly believed he was starting to feel like himself again, there’s something different about this stretch. Harkless just looks different.

“A little bit before the break, it seemed like he was just moving different on the court,” Damian Lillard said. “His activity level. His stamp on the game. I was starting to see it come along. I could just see how he was moving and the urgency and you could see that change in him.”

He started this trip with a solid performance at Brooklyn, recording 13 points, eight rebounds, four assists and one steal, then followed that up with a difference-making outing at Philadelphia, finishing with 13 points, five rebounds, three steals, two blocks, two assists. And while plus-minus can be a flawed barometer of a player’s worth, Harkless’ impact has been noticeable in that statistical category over the last four games, when he has recorded a plus-32, plus-22, plus-nine and plus-16.

Health has been the primary factor in Harkless’ resurgence — and it’s fair to wonder how much the addition of Rodney Hood has motivated him — but Harkless also said he’s also been inspired by a personal challenge to “set the tone” defensively from the opening tip. He certainly did that against Boston, gobbling up two steals in the game’s first five minutes as the Blazers opened with a little grit in a game that would prove to be a defensive slugfest.

“He was all over the place from the very beginning,” coach Terry Stotts said. “He got this hands on balls, he was aggressive going to the basket offensively, rebounded the ball. Obviously, he’s plus/minus speaks for itself. He had an outstanding game.”

Harkless doesn’t provide scoring outbursts like Lillard or CJ McCollum. He doesn’t command the paint like Jusuf Nurkic. He doesn’t bring flair off the bench like Jake Layman.

His value is measured by his ability to do a little bit of everything, to impact the game in so many ways. And he’s decided he can impact the final 21 games by inspiring his teammates through hustle and tenacity on defense.

“Over the break, we talked about kind of the way we’ve got to play moving forward and preparing ourselves for April,” Harkless said. “I think that’s something that I can take charge of on that end of the floor. Just setting the tone. I think have the ability to do it. I think guys look to me sometimes on that end of the floor, so it’s just something that I kind of want to lead by example.”

It’s been another roller-coaster of a season for Harkless. But, just as he has in the past, he’s rediscovering his mojo at just the right time.

“I think people judge him too much,” Nurkic said. “He was in and out (of the lineup) the whole season, never healthy the way he wanted. And now, when he’s full-time healthy, he’s doing a great job. On the defensive end, what he’s doing … is just tremendous for us. We (have to) keep trusting him.”

Joe Freeman | jfreeman@oregonian.com | 503-294-5183 | @BlazerFreeman | Visit subscription.oregonlive.com/newsletters to get Oregonian/OregonLive journalism delivered to your email inbox