PORTLAND, Ore. — Russell Westbrook will never admit to changing. That outward stubbornness is what's made him so successful, and so polarizing, over the first 11 years of his career.

Bring up his recent shooting struggles and changing offense, and he bristles. Ask him about his recent, noticeable improvements on the defensive end, and he'll insist it's nothing new.

"I've been able to switch and guard up through 4, sometimes 5s, since I've been in the league," Westbrook said Friday, ahead of the Oklahoma City Thunder's 111-109 victory over the Portland Trail Blazers.

Never before, though, has Westbrook defended like this. He is fourth among point guards in ESPN's defensive real plus-minus rankings. He's also leading the league in steals with 2.5 per game, besting his previous career high of 2.1 set in 2014-15.

Westbrook's defense has kept him productive even as he's in the midst of one of the most maddeningly inconsistent offensive stretches of his career. His 42.0 percent shooting from the field and 23.5 percent from three-point range are the worst they've been since his second season in the league, before he blossomed into the All-Star he's been for much of his career. He's never shot close to this poorly from the foul line (62.7 percent on 5.5 attempts per game).

Against Portland, he scored 31 points on 13-of-28 shooting; the game before, in a win over the Los Angeles Lakers, he finished with 14 points on just 3-of-20 shooting. Lately, his performances have often fallen under one of those two extremes.

It's this duality that's made Westbrook one of the most complicated and divisive figures in modern NBA history. 

His many fans point to the triple-doubles, huge scoring performances, outrageous fashion sense and unmistakable on-court passion and fury as reasons to love him.

To his detractors, he's an inefficient stat-padder whose presence, fun as it is to witness, is not conducive to winning basketball. Westbrook's defiance and reluctance to open himself up to the media and the public make him all the more inscrutable. Depending on your sensibilities, you can project onto him whatever you want, good or bad.

Westbrook's legacy and place in the league will only grow more complex as he ages out of the explosiveness that has thus far survived four knee surgeries in the past six seasons. That aging curve will be one of the most fascinating to witness over the rest of his career. The transition could be rocky, but his newfound defensive results are an encouraging sign of his ability to weather what will be a needed growth period.

Together with Paul George (having a season that's seen him garner MVP buzz), Westbrook is helping make the Thunder a terror for opposing offenses on the wing, despite the continued absence of injured defensive ace Andre Roberson.

Oklahoma City has the league's best defense, holding opponents to 102.2 points per 100 possessions, according to NBA.com. Following an 0-4 start to the season, the Thunder have found their footing and currently sit in third place in a tough Western Conference, just 2.5 games behind the first-place Denver Nuggets. That's due in no small part to Westbrook's improved instincts on that end of the floor.

"He's done a really good job of using his length," Thunder coach Billy Donovan said. "He's gotten into passing lanes, and he's gotten to good areas on the floor where he's been in help position. He's been disruptive. He's always been a physical guard, but even when he switches onto power forwards or bigger people, he can play post defense."

In his younger days, it was easy to mistake Westbrook's hyperactivity for good defense. The flashy steals that led to epic fast-break dunks have made him a SportsCenter staple. But throughout his career, the Thunder have been worse defensively with him on the floor. His gambling for steals hurt the team as much as they helped his highlight reel. This season, his steals are up, and this time they've come with smarter decision-making.

"It's his reads," Thunder center Steven Adams said. "On the gambling side of things, he makes a calculated decision about it. More calculated than just, you go after the ball, and if you don't get it, the play's completely screwed. You can't salvage the play. It's so tough. Both of them [Westbrook and George] are very selective about when they'll go and try to make a steal."

"There are other things he's doing that are impacting our team," Donovan said. "I think a lot of people are focusing on the shooting percentages. And I get it, because they've been drastically lower than what they've been in his career. But he's been rebounding, he's generating assists, and he's defending."

The relentless, unchanging playing style that has made Westbrook a force of nature for a decade is in the beginning stages of an evolution, one that will be necessary as his career advances. He turned 30 in November, and he's in the first season of a five-year, $205 million extension he signed in the summer of 2017, which will almost certainly keep him in Oklahoma City for the rest of his career.

For a franchise still reeling at the time from Kevin Durant's defection to Golden State, getting that kind of commitment from a fellow MVP and future Hall of Famer was a worthy cause for celebration. But the ink had hardly dried on the contract before cap-minded analysts and pundits began raising concerns about its long-term implications.

The notion that a player as reliant on his explosiveness as Westbrook—with this many miles on his surgically repaired knees—will be making $47 million at age 34 is a potentially dangerous one.

The next couple of seasons will be telling. It's not hard to picture a downside like the later years of Allen Iverson, a similarly talented and undersized one-man wrecking crew who electrified the league for a decade before falling off a cliff overnight as his athleticism left his aging body. By the time Iverson had been in the NBA as long as Westbrook has, he was a shell of himself, unable to accept a lesser role in a changing sport, and he was out of the league by age 34.

That's the worst-case scenario. But for every Iverson or Carmelo Anthony, there are touchstones for Westbrook to lay out a more optimistic blueprint.

Jason Kidd developed a three-point shot in the second half of his career, which allowed him to age gracefully and remain productive until he retired at age 39. Kidd's 1994-95 co-Rookie of the Year, Grant Hill, was likewise able to adjust his game as years of injuries caught up to what was once one of the most electrifying high-flyers in the sport. Hill stuck around until his 40th birthday and remained a valuable role player to the end.

Vince Carter, too, is providing a roadmap for how a player like Westbrook can navigate his advanced years. Two decades ago, Carter captivated the NBA as a dunking phenom and freak athlete, not unlike the presence Westbrook has held in the league.

Those days are well in the past, but Carter long ago reinvented himself and his game, becoming a savvy defender and reliable outside shooter. He's still in the league at age 41 (42 on Jan. 26), in his 21st season, playing 17.5 minutes per game off the bench for the Atlanta Hawks.

Whether Westbrook hangs around into his 40s, those around him are optimistic that he'll be able to adjust and adapt as he transitions from "superstar" to "aging former star."

"He's really, really bright," Donovan said. "Just being around him now, this being the fourth year, it seems like every year he comes in, there's always different things that he improves upon and things that he gets better at. And I think as the game evolves, he'll evolve and he'll figure out different things he needs to do to grow and get better as a player.

"That's the one thing I respect about him: The guy's been an All-Star for six or seven years, but he's always eager to get better, and I really admire that about him. His willingness to want to try to improve."

The Thunder have made the playoffs in eight of Westbrook's 10 full seasons, including a Finals appearance and four Western Conference Finals trips. Since Durant's departure in 2016, however, they haven't advanced past the first round, and much of the public blame has fallen on Westbrook.

This season, he has an ideal running mate in George, who is playing better than he ever has in his ninth season. It's not quite Durant, but it's close enough to inspire hope that the Thunder will be able to survive Westbrook's shooting struggles and keep themselves relevant well into April and May.

"Any player at his level, to get to that level, you have to go through some adversity, and he's dealt with that," Donovan said. "The biggest thing for me is encouraging him. He's getting good looks, and he's taking good shots, and he's getting everyone else involved."

Thus far, Westbrook's inconsistent offense hasn't slowed the Thunder down, and his defense has played a significant role in their success. The beginning stages of his evolution and reinvention are starting to show themselves, and the shape his growth takes will define the next chapter in one of the most memorable careers the sport has seen.

Sean Highkin covers the NBA for Bleacher Report and is currently based in Portland. Follow him on Twitter, @highkin.