The 2021 MLB season is still in its infancy. But that doesn't mean teams are not expecting more from their additions and impact players. 

So let's take a closer look at some of the more notable busts. In this case, a "bust" can entail signees from this past offseason and players on big contracts. It might also include players who appeared ready for star turns in 2021 but instead have had a tough time recapturing success.

An important consideration: We will exclude players who have yet to play or have been severely limited with injuries. Otherwise, it'd be easy to throw the likes of Kirby Yates, Trevor Rosenthal and George Springer (among others) under the bus.

Sound good? Here we go.

A Trio of Mets

Plenty of New York Mets position players have disappointed. But three guys—Francisco Lindor, James McCann and Jeff McNeil—are worth pointing out.

Lindor is providing his usual premium defense. He ranks in the 99th percentile in outs above average (OAA). However, the Mets did not give Mr. Smile that $341 million contract extension merely for his glove. They very likely expect him to be one of the best hitters in the lineup. He hasn't been.

The 27-year-old is slashing .212/.321/.273 with just two extra-base hits. He ranks in the 15th percentile in expected slugging (xSLG) and just the sixth percentile in barrel percentage.

McCann is another offseason acquisition who has disappointed. He was an All-Star in 2019 and posted an .896 OPS in 2020. But he has just a single extra-base hit and ranks in the 15th percentile in expected wOBA (xwOBA). McCann is also among those without a single barrel (min. 25 batted ball events). New York needs more from a guy it signed to a four-year, $40.6 million contract in free agency.

Lastly, Jeff McNeil is going through it to start the season. McNeil was an All-Star in 2019 and hit .311 with an .836 OPS last season. He is hitting just .196 with a .634 OPS in 2021, and his weak contact rate has nearly doubled from 2020.

Marcell Ozuna, Atlanta Braves

The good news is Marcell Ozuna is still drawing his walks. The bad news is he's striking out more and not hitting the ball as hard.

Ozuna ranked in at least the 94th percentile in barrel rate, average exit velocity and hard-hit rate in 2020. Although he ranked in just the 21st percentile in whiff rate, Ozuna ranked closer to league average in strikeout rate. As a result, he led the National League in homers (18) and total bases (145) last summer.

However, like many of his Atlanta Braves teammates, Ozuna has struggled this season. He is slashing .186/.293/.233 with a 43 OPS+ and ranks in the 29th percentile in terms of strikeout rate. 

The batted-ball metrics have seen a bit of a decline. Ozuna's average exit velocity is down 3 mph from 2020. His hard-hit rate has fallen from 54.4 percent last season to 39.0 percent this year, and the barrel rate has been more than cut in half. 

Two things of note: Ozuna is struggling against the fastball (.167 average) and is hitless against left-handed pitchers (18 at-bats) this season. He hit .400 against the fastball and slugged .867 against lefties in 2020. 

Dansby Swanson and Travis d'Arnaud have been disappointing after strong 2020 seasons. Left-handers Max Fried and Drew Smyly have dealt with injuries and ineffectiveness.

But Atlanta signed Ozuna to the fourth-largest contract among position players in terms of guaranteed value at $65 million. The Braves could use a return to 2020 form.

Maybe Ozuna will get it going after homering on Wednesday.

Patrick Corbin, Washington Nationals

Washington Nationals left-hander Patrick Corbin was a vital piece of the 2019 World Series champions. His ability to start and come out of the bullpen for high leverage was huge in October. It almost seemed to validate the entirety of his six-year, $140 million contract.

Almost.

The past couple of seasons have been nightmarish for Corbin. He allowed an MLB-high 85 hits and had a 4.66 ERA in 2020. Things have been far worse this spring, as Corbin has a 10.47 ERA and 2.02 WHIP. What's happened to him?

The 31-year-old is having a tough time getting whiffs, in part because his slider has not been nearly as dominant as it was in 2019. Corbin's slidergenerated a 51.4 percent whiff rate and .204 xwOBA that year. But opponents have a .300 xwOBA against the slider in 2021, with the whiff rate falling to 36.2 percent. The spin rate has also decreased.

Moreover, Corbin has dealt with command issues. He has 10 walks in just 16.1 innings. Homers have been another problem, as he has already given up six.

Again, some Nats fans might feel Corbin's role on the 2019 championship team alone practically made signing him to that enormous deal well worth it. But Washington kind of needs him—and Stephen Strasburg—to be a horse, especially with Max Scherzer's impending free agency.

Corbin has had a hard time simply commanding the zone and getting outs, much less being a front-line guy.

Luis Castillo, Cincinnati Reds

Luis Castillo seemed destined to entrench himself among baseball's elite aces heading into 2021.

The Cincinnati Reds right-hander was a force in 2020, posting a 3.21 ERA and a career-high 2.65 fielding independent pitching mark (FIP) in 12 starts. He struck out 11.4 opponents per nine innings, dominating hitters with a tremendous fastball-changeup combination. 

However, Castillo has not resembled anything close to an ace in 2021.

The 28-year-old has a 6.29 ERA and 1.60 WHIP in five starts. He is striking out just 7.0 hitters per nine innings. The underlying numbers are not great, either. Castillo ranks in just the 35th percentile in xwOBA and 26th percentile in whiff rate. Castillo's inability to get whiffs is especially notable. His velocity is down about 2 mph on all four of his pitches.

There are some encouraging signs. Castillo's ground-ball rate is still over 55 percent, and the weak contact is actually up slightly from 2020. But the barrel rate has nearly doubled, with the average exit velocity up 4 mph.

Perhaps Castillo will find added life as the weather heats up. He likely needs to in order to ignite his swing-and-miss stuff and rediscover the form that made him one of the NL's best pitchers in 2020.

Amir Garrett has been astoundingly bad for the Reds. Eugenio Suarez has not gotten it going offensively and has not adjusted well to shortstop. But Castillo's struggles are the most befuddling.