At its core, baseball is a game of peaks and valleys. Even the best to ever play the game are going to struggle from time to time. But if you're going to pick and choose when the struggles come, the beginning of the season is one of the least opportune times. Reigning NL Rookie of the Year Corbin Carroll is learning this the hard way.

When a player or a team gets off to a slow start, it can feel like it's never going to end. You look up at the scoreboard and your batting average starts with a one. Or it's the end of April and you still have a single digit in the win column. Even if you play your normal standard of ball for the rest of the season, MLB is cruel and unforgiving when it comes to slow starts.

And in a month full of surprises, these five players, teams and position units have been the biggest disappointments of all. Let's examine why everything seems to be going wrong and how they each might be able to climb their way out of the holes they've dug before it's officially too late.

Corbin Carroll, Diamondbacks

It makes almost no sense how a player who unanimously won Rookie of the Year, finished fifth in MVP voting and became the first rookie ever to hit 25 home runs and steal 50 bases could be so dreadful in the first month of his age-23 season. But Corbin Carroll, who was due for a little bit of regression based on his batted ball metrics, has gone completely south and he's dragging the entire Arizona Diamondbacks‘ lineup down with him.

Among 183 qualified hitters across MLB, Corbin Carroll ranks 166th with a .189 batting average and 178th with a .236 slugging percentage. He's in the bottom one percent of all hitters in average exit velocity and the bottom three percent in hard-hit rate.

He looks totally lost in the batter's box right now and D-Backs manager Torey Lovullo, who was hoping to set and forget Corbin Carroll as his number two hitter this season, has had to drop his young star to the seven or eight spot in the lineup most days.

Whatever reasons there may be for Carroll's struggles (fatigue from a long postseason run, lingering concerns about his shoulder injury from last July, inability to catch up to high velocity), the D-Backs can't afford to sit around all season waiting for 2023 Corbin Carroll to show up. This is a team with championship aspirations and those are centered around Carroll being the engine that makes the lineup go. He needs to start driving the ball with authority again, and quickly so.

Houston Astros

Houston Astros second baseman Jose Altuve (27) is congratulated by manager Joe Espada (19) after hitting a home run in the third inning against the Colorado Rockies during the MLB World Tour Mexico City Series game at Estadio Alfredo Harp Helu.
Kirby Lee-USA TODAY Sports

There were too many things going wrong with the Houston Astros to single out one player or even a position group, so let's just lump the whole team into a heaping pile of disappointment. Two wins over the miserable Colorado Rockies in Mexico City were an absolute necessity, but at 9-19, the Astros have still done a lot of damage to their postseason hopes this early on.

Though the Astros still rank 7th in team OPS, their offense is still full of underperforming veterans, chiefly José Abreu and Alex Bregman. Neither has hit a home run and Abreu has been the least valuable player in the league by fWAR with a shocking -1.2. Bregman, for his part, is at 0.1.

But the offense doesn't hold a candle to the disappointment of the pitching staff. The Astros have the fifth-worst team ERA in the league, are 20th in starting pitcher fWAR and 24th in relief pitcher fWAR. For a team that has had historic sustained success as a pitching staff for nearly a full decade, that's a shocking step backward.

Yes, it's just a month, but if you can't catch the Oakland Athletics or the Los Angeles Angels at the end of that month, something is very wrong. The Astros have all the veteran leadership and talent they could ask for in their locker room, but solutions need to start presenting themselves before this season, in which Houston has its highest payroll by far in franchise history, becomes a total failure.

Vladimir Guerrero Jr., Blue Jays

There are other hitters having worse seasons statistically, but Vladimir Guerrero Jr. has to be considered one of the biggest disappointments in the sport from a narrative perspective. Not only because of his struggles in 2024, but the slow and steady decline his career has undergone since his brilliant age-22 season in 2021.

Guerrero's OPS+ has gone from an elite 167 in 2021 (67% above league average, for reference) to 133 the following year, then 117, and now 93. He makes tantalizing hard contact but seems to do most of it on ground balls, which are rarely worth much on the scoreboard.

Ever since the Blue Jays stopped playing their games in Dunedin, Florida during the 2021 pandemic restrictions in Canada, he's struggled to hit for power in his home ballpark. The Jays need Vladdy to carry the team offensively and instead, he's hampering them.

And it isn't just the struggles at the plate that are causing gray hairs among Blue Jays fans. He dropped a chest-high throw from Isaiah Kiner-Falefa that single-handedly blew a game for the Jays in Kansas City. He got picked off first base on Sunday despite being a total non-threat to steal second. These mental lapses are inexcusable for anyone, but for a presumed franchise player looking for a long-term extension, they're unfathomable.

Miami Marlins pitching staff

Miami Marlins starting pitcher Max Meyer (23) pitches against the Atlanta Braves in the first inning at loanDepot Park.
Jim Rassol-USA TODAY Sports

Even when the Miami Marlins were non-contenders in the 2020s, they were known for producing quality young starting pitchers. Sandy Alcantara, Pablo López, Jesús Luzardo, Eury Pérez, the list goes on. In 2024, the Marlins were coming off a postseason berth and the hope was that even with a somewhat light-hitting offense, the pitching could still carry them back to October. Instead, the entire staff has imploded.

Injuries are a huge culprit here and that's mostly out of the Marlins' control, so it's not entirely fair to say Miami failed in putting this staff together. But Luzardo was struggling mightily before he became the latest injury victim over the weekend, the A.J. Puk starting pitching experiment turned out dreadfully and the team sent its only promising starter, Max Meyer, down to AAA to maintain an extra year of his service time.

As of Monday, the Marlins officially have the worst record in MLB at 6-23, one more loss than the Chicago White Sox, who were off to the worst 25-game start in franchise history.

Tampa Bay Rays outfielders

In 2023, when the Tampa Bay Rays were up to their usual tricks, winning 99 games with a roster full of castaways and ‘who's that guy,', the outfield was a consistent bastion of excellence. Between Randy Arozarena, Josh Lowe, Jose Siri and Luke Raley, the Rays got 87 home runs and a combined 10.4 bWAR. Kevin Cash had to be loving life knowing that whatever combination he wrote on the lineup card was likely to work.

This season, nothing has worked at all. Arozarena and Siri are the two main holdovers and both have a slugging percentage under .300, in the bottom 13 of all hitters. Lowe has yet to play a game this year due to injury, while Raley is off to a terrible start… as a Seattle Mariner. Of all people, converted former shortstop Amed Rosario has been by far the team's best-hitting outfielder, though his production has already started to slump during the team's recent skid.

A team like the Rays is unlikely to ever have transcendent stars in the outfield, since top prospects typically come up as infielders. They rely on the Arozarenas of the world to play above their expectations and so far, that's gone in the opposite direction. Though it seems like the Rays find a way to cobble together a winning record every year, this will be the year Tampa finally bottoms out if the outfield can't carry their weight offensively.