Generally, players will get better the longer they stay in the NBA. They get the opportunity to train with the best basketball coaches and use the most advanced facilities in the world to improve their craft. Most of the time, they do just that. Improvements can be seen in players' better shooting splits, increased stat lines, or simply more minutes. The NBA's Most Improved Player Award serves to reward the individuals who've made these types of jumps.

In this piece, however, we take a retrospective look at the players who went the opposite way. These players came into the league guns blazing, but have since failed to live up to the early promise and have unexpectedly declined. We will be looking at their rookie years, as well as what they have gone on to do (or not do) since.

With, that, let's get into the players who peaked in their rookie years.

Dennis Smith Jr.

Rookie Year Stats: 15.2 points, 3.8 rebounds, 5.2 assists

The most recent one on this list.

Dennis Smith Jr., coming out of the North Carolina State University, legitimately looked like one of the most exciting rookies in his rookie class. As a rookie, DSJ was a fun-to-watch hyper-athletic point guard with a lot of potential upside. He built momentum all throughout his first year, competing in the dunk contest and eventually getting All-Rookie Second Team honors.

DSJ became one of the Dallas Mavericks' most valuable assets, despite taking a back seat to Luka Dončić in his sophomore year. The former would be Dallas' biggest piece in the blockbuster Kristaps Porziņģis trade, which sent him to the New York Knicks. The organization had hoped for him to be their point guard of the future.

In New York, however, everything seemed to go wrong as he did not progress as expected; his mediocre outside shooting became worse, and he continued to be an unwilling defender.

DSJ's minutes slipped down from almost 30 minutes a game all the way to around 15 minutes a game. His game time went as low as 9 minutes a contest before eventually getting traded to the Detroit Pistons for Derrick Rose. While with the Knicks, Smith Jr. only averaged 7.7 points on poor shooting splits.

Pretty disappointing so far, but the North Carolina native still has a chance to turn his career around with his new team.

Michael Carter-Williams

Rookie Year Stats: 16.7 points, 6.2 rebounds, 6.3 assists.

There's a long, long line of players who were tipped to be the next Magic Johnson: unusually tall, fast, and athletic playmakers tend to get this distinction. It's happened to guys like Shaun Livingston, LeBron James, and Ben Simmons. The 2013 Draft's version of this unique breed of player was Michael Carter-Williams.

MCW's draft class looks good today, with guys like CJ McCollum, Victor Oladipo, Rudy Gobert, and Giannis Antetokounmpo coming good a bit later in their careers. Carter-Williams, in contrast, stood out pretty early on. In his first game, he recorded a stat line of  22 points, 7 rebounds, 12 assists, 9 steals, the most steals in one game by a rookie in NBA history.  He would win a total of three Rookie of the Month awards, the most in Philadelphia 76ers history, on his way to winning the 2014 Rookie of the Year award.

There was no reason to believe that those stats would be as good as it gets for MCW, but that was exactly what happened. As a rookie, he averaged a 16-6-6 line, which was only accomplished by Magic Johnson and Oscar Robinson prior to Carter-Williams. His stat line has since stagnated and gone down, however, only averaging about 9 points, 4 rebounds, and 4 assists after his historic rookie season.

A silver lining is that the now-Orlando Magic has always been a good perimeter defender, which should keep him somewhat valuable in the league. Additionally, he has been picking up more minutes for his new team, due to Markelle Fultz's season-ending injury. Nevertheless, he is quite far removed from the outstanding rookie that he was in Philly.

Jahlil Okafor

Rookie Year Stats: 17.5 points, 7.0 rebounds, 1.2 assists

It's quite easy to see where things went wrong for Jahlil Okafor, but more on that later.

The Nigerian-American was one of the most dominant players in his High School class, after which he played an amazing freshman year with Duke University. This led him to get selected 3rd overall in the 2015 NBA Draft.

He put up 17.5 points a game in his rookie year, more than the likes of Kristaps Porziņģis, Devin Booker, and Nikola Jokić, and second only to Karl-Anthony Towns. The two centers were actually on a relatively equal footing at the time.

Towns has gone on to be a 2x All-Star and the best shooting big man in history; Okafor's career, meanwhile, has gone downhill from his rookie year.

Okafor is a back-to-the-basket player who thrives in the post, while Towns is a much more versatile offensive player, able to score on all three levels. The reality is that the league has simply evolved past centers like Okafor, who cannot operate more than three feet away from the basket.

He's been averaging just below 9 points and 5 rebounds a game since his rookie year while playing just 10 minutes per contest this season (just a third of his game time as a rookie).

After hitting a brief patch of good form with the New Orleans Pelicans two seasons ago, he is currently riding the Detroit Pistons bench.

O.J. Mayo

Rookie Year Stats: 18.5 points, 3.8 rebounds, 3.2 assist

How exactly did a talented guard-forward end up being a basketball journeyman?

O.J. Mayo started out on fire in the NBA, averaging an impressive 18, 3, and 3 in his rookie season. He came second only to the soon-to-be MVP Derrick Rose in Rookie of the Year voting, finishing higher than the likes of Russell Westbrook and Kevin Love. The 2008 3rd overall pick seemed to be destined for big things.

However, a string of off-court issues proved to be his undoing.

In his sophomore season, he was issued a 10-game suspension for violating the NBA's anti-drug program. He was also involved in an altercation with then-teammate Tony Allen earlier in the season. O.J. would eventually get banned from the league altogether due to another drug violation. It is worth noting that he was still averaging respectable stat lines and minutes at the time, although he was not nearly as good as his first-year self.

He would play in Puerto Rico, Taiwan, and China thereafter. As of now, he is playing for the Liaoning Flying Leopards in the Chinese Basketball League. He is currently one of the best players in China, averaging close to 24 points and 6 rebounds in two seasons.

Sadly, no NBA team has taken a chance on the 33-year old veteran, despite being eligible to play in the NBA again in the 2018-19 season.

Tyreke Evans

Rookie Year Stats: 20.1 points, 5.3 rebounds, 5.8 assists

In a rookie class featuring the likes of DeMar DeRozan, James Harden, and Stephen Curry, it was Tyreke who stood out the earliest. His rookie year was said to be the best one since LeBron James'; in fact, Evens is only one of four rookies to put up 20-5-5, the other three being Oscar Robertson, Michael Jordan, and James himself.

So what's happened since?

Tyreke Evans was a dominant force and a matchup nightmare as a 6'6” slasher at the point guard position. The 1 was clearly his best and most comfortable position. However, the Sacramento Kings saw it fit to move him to the wing to play shooting guard and small forward, which meant that he had less of a matchup advantage. He was also expected to be a better shooter on the wing, which didn't play to his strengths. He would average a lower 15.4 points on 44% shooting from the field and 30.2% from three for the next 8 seasons, playing for both the Kings and the New Orleans Pelicans

His fortunes looked to change in the 2017-18 season with the Memphis Grizzlies, however. He was finally allowed to play the point guard position again after an injury to Mike Conley. This coincided with Evan's best scoring season since his rookie year, with 19.4 points on 45.2% shooting from the field and almost 40% from three.

Evans would then get traded to the Indiana Pacers to play back-up to Darren Collison. He was still averaging a decent 10-3-2 off the bench. However, he would ultimately get banned from the league until 2021 for violating the NBA's anti-drug program.

Tyreke averaged decent numbers all throughout his career, but his rookie year numbers looked like that of an eventual all-time great. He is a testament to how bad man-management (and unfortunate circumstances) can ruin a potential Hall-of-Fame career.