The average progression of an NBA career features incremental annual improvement that leads to a peak stretch (right around the mid-to-late 20s), and then inevitable decline before retirement.

Players grow, thrive then fade. It's the circle of NBA life. 

Sometimes, for whatever reason, verified talents peak before they can reach their full potential, be it due to poor health, a trade or a simple inability to develop their game. These situations can be disappointing and even sad.

But they also highlight how ridiculously difficult it is to have a long, fulfilled NBA career. Here's a look at seven players who qualify. Each of them accomplished quite a bit, but they also left plenty of individual production on the table. Most either played on an All-Star team or won a major award before their 25th birthday, then either dramatically declined or failed to improve in any noticeable way. 

There are no anomalous breakout years, but instead a clear uphill trajectory before unexpectedly leveling off. They're listed in alphabetical order. 

Tyreke Evans

Tyreke Evans' first season was as anomalous as it was impressive.

He averaged over 20 points, five rebounds and five assists per game, becoming just the fourth rookie in NBA history to do so (the other three are Michael Jordan, Oscar Robertson and LeBron James).

While that trio will go down as top-10 world-beating Hall of Famers, Evans' career has stumbled downhill ever since. He's never tallied more win shares than in that first season. A score-first point guard in a small forward's body, Evans has the unteachable ability to create a decent shot for himself or a teammate at will.

But he can't shoot, doesn't always try that hard on defense and...can't shoot.

Career 29 percent three-point shooters—who aren't All-Defensive Team selections—will struggle to find a home and role in today's NBA, and Evans has yet to adapt.

Dwight Howard

It's a little unfair to include Dwight Howard on this list because he's still a borderline All-Star in his 13th season.

But Howard's best years were during his early 20s, when he was hands-down the best center in the league and led the Magic to a Finals appearance in 2009 (when he was just 23).

Howard's statistical drop is due to a steady physical decline accelerated by back and knee surgeries, and he couldn't add new elements to his game as he aged. His post moves remain as rigid as ever, and Howard never developed any touch outside the paint or made a smooth transition into a consistent roll man.

He still rebounds at a high rate, particularly when a teammate misses a shot. But as good as he was when this decade began, Howard's refusal to diversify his skill set has led to consistent offensive struggles as the league evolves around him.

Forcing his way from one city to the next didn't help. Howard demanded a trade from the Orlando Magic, took less guaranteed money to spurn the Los Angeles Lakers as a free agent and then split with the Houston Rockets after he couldn't get along with current MVP candidate James Harden. 

Who knows how long he'll last with the Atlanta Hawks?

Serge Ibaka

Ibaka led the league in block rate when he was 22 years old. It was the same season Oklahoma City came within three wins of a world championship, in part because it was Ibaka's first as a full-time starter.

He developed into a legitimate stretch 4 over the next few seasons, starting in the corners before emerging as a useful above-the-break weapon in 2015. His percentage of three-pointers launched from the corner was 81.7 percent in 2014, and plummeted down to 18 percent the following year, per Basketball Reference.

Playing alongside Kevin Durant and Russell Westbrook—two cyclones responsible for a vast majority of the Thunder's shot creation—Ibaka was a third wheel who knocked down open shots, protected the rim, set screens and rebounded the ball.

Given his athleticism and rapid development, imagining Ibaka doing more with a larger role was always a fun hypothetical. Then he was traded to the Orlando Magic on the night of last year's draft and the questions were answered: Not only does Ibaka still struggle to create his own shot—either in face-up situations or with his back to the basket—but his rim-protection numbers have started to descend.

That 9.8 percent block rate that led the league five years ago? It's currently at 4.2 percent. Opponents are shooting 53.4 percent at the rim when he's nearby, which is 12.6 percent higher than it was in 2015.

Ibaka can still shoot, but so can plenty of big guys around the league. If he isn't protecting the paint at an elite level, he becomes an average power forward.

Kevin Love

Love was widely accepted as a top-10 player three years ago. He averaged over 26 points, 12 rebounds and four assists per game, a feat only matched by six other players in NBA history (Kareem Abdul-Jabbar, Wilt Chamberlain and Oscar Robertson are three of them).

Love could shoot threes, and he owned the glass as the hub of Minnesota's top-10 offense—a playmaking savant who commandeered a read-and-react attack from the high post as well as any contemporary centerpiece could.

But a combination of iffy health and a dramatic change of scenery have detoured Love's career from perennial All-Star to glorified (yet extremely important) role player.

Love is still good as the third-best player on his own team, a group that just so happened to win it all last season. But a new set of responsibilities have restricted him in several ways. He's one of the better offensive players in the league, and Cleveland does a good job leveraging his strengths in the post—as well as his spot-up ability—but there's been a noticeable (and understandable) statistical regression since his transcendent campaign in 2014.

This is almost entirely due to a decrease in shots and the necessity on offense to stray away from the basket. Love led the league in offensive rebound rate his first two years (15.1 and 14.5 percent, respectively). Two seasons ago, his offensive rebound rate plummeted to 6.5 percent.

Most of this is the tax for playing beside LeBron James and Kyrie Irving. Love deserves credit for necessary adjustments and sacrificing individual acclaim for the greater good. But it's impossible to say he's a better or more complex basketball player at 28 than he was at 25.

Derrick Rose

Everyone knows why Derrick Rose is on this list.

He's the most recognizable basketball tragedy of his generation, the youngest MVP in NBA history and the only winner of that award who won't be enshrined in Springfield, Massachusetts.

Knee injuries robbed Rose, the Chicago Bulls and basketball fans everywhere of a thrilling career. Think Russell Westbrook but with tighter gears. Rose was an explosion in 2011, a combustible darling who single-handedly balanced Tom Thibodeau's defensive system with a reliable offensive bite by slicing through the paint whenever he felt like it.

He averaged 25 points per game on 44.5 percent shooting that year. Four years later, he was down to 17.7 points at a 40.5 percent clip.

Several serious injuries domesticated Rose's savage athleticism and infiltrated his psyche. That same aggressiveness remains in bits and spurts as he tries to have a positive impact on the New York Knicks. But it isn't good enough on most nights. 

His inability to develop a consistent three-point shot has lowered his post-torn-ACL ceiling, and nothing he does for the rest of his career will touch those magical first few seasons.

Deron Williams

Nine years ago, it felt like Deron Williams would be on the Utah Jazz forever. He was one of the best point guards in the league, a pick-and-roll commandeering bruiser who punished smaller defenders one-on-one as often as he set teammates (like Carlos Boozer) up with good looks at the basket. 

But after a three-year span from 2008 to 2010 in which he was the only NBA player to log at least 4,000 points and 2,300 assists, Williams was traded to the New Jersey Nets for Derrick Favors and picks in a shocking deal that ultimately derailed his career. 

Williams battled wrist and ankle injuries during three-and-a-half years with the Nets before he was eventually waived by the team in 2015. His hometown Dallas Mavericks scooped him up three days later, only to waive him a few days ago. 

He's a three-time All-Star who can still contribute at a decent level, but looking back at where he was in his age-23 season (18.8 points, 10.5 assists, 20.8 player efficiency rating and 59.5 true shooting percentage), it's incredible to watch the depths of his nosedive.

Here's what Ken Berger wrote for CBSSports.com back when the Mavericks picked Williams up: "That's how far the 31-year-old Williams has fallen. For a player once so dominant and electrifying that he stood toe-to-toe with—and, at times, towered over—Chris Paul in the debate over who was the best point guard in the NBA, serviceable is now the goal.

"I don't think he'll be an All-Star again because of how good the West guards are," one longtime executive told Berger. "I don't think he's a top-15 point guard right now, but I think he can eventually get there.'"

He will now back up Kyrie Irving on the defending champion Cleveland Cavaliers.