In professional sports, it’s tough to stay on top for long. Sure, there are players like LeBron James who dominate their field for over a decade. But for most pro athletes, success is fleeting. Each year, in every sport, there are hundreds of young, driven athletes hoping for a shot at the league, looking to take someone else’s spot on the roster.

Even if an athlete has a stellar season, there’s no guarantee it will last. Hockey, football, baseball, and basketball are all team sports, and changes in coaches or players can have huge impacts on the players. If two players have great on-field chemistry but one leaves in a trade or free agency, the other’s game could slip.

Injuries are also a constant worry for players. Just about every pro athlete plays through various bumps and bruises throughout the season. And even if an athlete can play through the pain, they may not be as effective due to a pulled muscle or sprained ankle.

Being a pro athlete is unlike many other jobs because all players have a relatively short window where they can be successful. Athleticism fades over time, no matter how well an athlete stays in shape. No matter how good players are in their prime, father time is undefeated. Eventually, each athlete will have to hang up their shoes, spikes, or skates.

Click here to see 25 athletes who were huge disappointments in 2017.

Dak Prescott made the Pro Bowl as a rookie quarterback for the Dallas Cowboys in 2016 and it looked like he would be a star for years to come. But Prescott couldn’t replicate that success in his sophomore season. The Cowboys’ dominant offensive line had to replace two starters from 2016, and running back Ezekiel Elliott was suspended for six games because of off-field issues. Without those key teammates, Prescott took a big step back from where he was as a rookie.

Sidney Crosby is still one of the best players in the NHL, but he’s not immune to a falloff in production. Crosby is on pace to have one of his lowest goal totals in a full season and his lowest assist total ever. This could be a result of the overall poor quality of play from the Penguins this season. The back-to-back Stanley Cup champions are next to last in the Metropolitan Division this year and could miss the playoffs unless their play improves.

New Los Angeles Laker Lonzo Ball has been one of the most hyped players to come to the NBA in recent memory. Because of his superior court vision and headline grabbing father LaVar, Lonzo Ball is the subject of intense scrutiny. Despite being selected with the second overall pick, Ball hasn’t been able to live up to his lofty expectations. It’s obviously too early to label a 20-year-old a bust, but 31 games into his pro career Ball is shooting below 35% from the field and an embarrassing 48% from the free throw line.

Albert Pujols has been one of the best baseball players in the history of the game. But it appears that his age is catching up with him. Throughout his 20s, Pujols hit over .300 with 30 home runs every season. In recent years, however, Pujols’ batting average has started to slide. In 2017, Pujols hit a career-low .241. In addition to diminished production at the plate, Pujols rarely plays first base for the Los Angeles Angels, instead playing as the designated hitter.

The 25 players on this list are athletes in one of the four most-watched leagues in the United States — the NHL, the NBA, the MLB, and the NFL. The players who made this list significantly underperformed compared to their previous professional seasons, or, if they are rookies, haven’t played up to the expectations of their draft positions. For the NHL and NBA, only the 2017-2018 season was considered. Players who missed extended time with injuries or suspensions were not considered.