Some hitters rake from pretty much their first day in the big leagues. In recent seasons, precocious talents such as Ronald Acuña Jr., Pete Alonso, Cody Bellinger and Juan Soto have immediately announced themselves as stars.

But more often, finding your footing against Major League pitching takes time. It requires players to adjust, and teams and fans to exercise patience. The rewards can be sweet, though.

So who might make that jump in 2021? MLB.com convened five reporters to draft 10 candidates -- five from the American League and five from the National League. While “breakout hitter” could have a number of definitions, we stuck to the following criteria:

• Entering age-27 season or younger
• At least 100 career MLB plate appearances (so no top prospects, such as Wander Franco or Jarred Kelenic)
• No previous All-Star selections or seasons with at least a 120 OPS+ (min. 100 PA)

Here are the selections:

AMERICAN LEAGUE

Luis Robert -- OF, White Sox
Key number: 9 batted balls with 110+ mph exit velocity

Yes, I’m fully aware that Robert struck out in roughly one-third of his plate appearances last September, nosediving his early bid for the AL MVP. Chases and whiffs aren’t going to suddenly disappear from Robert’s game, but I’m choosing to view those struggles in a shortened season as a plus for ‘21. He packed all the ups and downs into 60 games, preparing him for the rhythms of a 162-game grind. And, to put it simply, Robert is simply too talented to stay down for long.

Robert is capable of tape-measure blasts (see: that 487-foot moonshot in the AL Wild Card Series), but, more importantly, he consistently scalds the ball. His nine batted balls with a 110-plus mph exit velocity put him in company with superstars like Marcell Ozuna, Corey Seager, Giancarlo Stanton and Ronald Acuña Jr. last year. That’s the kind of power La Pantera can tap into, and it's why I think he could rack up 25-30 homers as a force for those dynamic White Sox.
-- Matt Kelly

Vladimir Guerrero Jr. -- 1B/DH, Blue Jays
Key number: 12 career batted balls with 115+ mph exit velocity

Even though we’ve already seen two seasons of Vlad Jr., it’s easy to forget that he’s still very young -- he’ll be 22 by Opening Day, with plenty of career ahead of him. We’ve seen the impressive power, and there’s a lot of evidence that there’s even more waiting to be unlocked. His 12 batted balls with at least a 115 mph exit velocity since he debuted are five more than any other player has since the start of 2019.

In 2020, Guerrero had a 50.8% hard-hit rate, which ranked 12th among players with at least 100 batted balls and was up about 12 percentage points from '19. As with all ‘20 stats, the real number for him over a full season likely lies somewhere in the middle, but this shows that there’s plenty of power for the young slugger still to unleash. The key will be lifting all that hard contact in the air on a more regular basis. The Blue Jays added veteran George Springer in the offseason, and with a lot of other talented teammates including Bo Bichette, Cavan Biggio and others, Guerrero Jr. should be ripe to break out in 2021.
-- Sarah Langs

Franchy Cordero -- CF, Red Sox
Key number: Career 12.4% barrel rate

Cordero has amassed just 315 plate appearances in four big league seasons, missing significant time with a right forearm strain, a right elbow sprain and a fractured right hamate bone. But in that small sample size, the 6-foot-3, 226-pound slugger has shown some impressive raw power. Nine of Cordero’s 12 career homers have traveled 420 feet or more, including a 489-foot blast in 2018 that is tied for the 12th-longest homer in Statcast history (since 2015).

The 26-year-old has recorded 22 barrels (batted balls with the optimal combination of exit velocity and launch angle) as a big leaguer, with a 12.4% barrel rate. To put that in perspective, only 30 qualified hitters had a barrel rate of 12.4% or better in 2020. Cordero has shown a tendency to swing and miss, but after recording a 38.4% whiff rate and a 38.8% strikeout rate in his first three seasons, he lowered those marks to 20.2% and 9.5%, respectively, in 2020. It’s unclear how much playing time Cordero will get after being traded from the Royals to the Red Sox last week, but it will be fun to watch him take aim at Fenway Park’s famous red seats in the right-field bleachers this season.
-- Thomas Harrigan

Nate Lowe -- 1B/DH, Rangers
Key number: 11.9% career barrel rate

A change of scenery might be just what Lowe needed. Between 2018-19, the 6-foot-4, 220-pound, left-handed slugger slashed .282/.401/.497 with 20 homers in 121 games at Tampa Bay’s Triple-A Durham affiliate. But Lowe had trouble sticking on a deep Rays’ roster, collecting 245 plate appearances in 71 games across a number of different MLB stints in 2019 and ‘20. A December trade to Texas presented the 25-year-old with a golden opportunity. “We made the deal with the expectation and hope that Nate would lay claim to the job,” said Rangers president of baseball operations Jon Daniels. There will be competition with Ronald Guzmán, among others, but a regular role is there for the taking.

It’s not as if Lowe was a bust with Tampa Bay, either. He posted an above-average 107 OPS+ in both 2019 and ‘20, hitting a collective .251/.322/.447 with 11 homers. That’s nothing special for a player at his position, but there are signs of better days ahead. With Lowe’s ability to make hard contact and lift the ball, his barrel rate ranked 54th of 452 hitters with at least 100 batted balls over those two seasons. One big question is whether Lowe can complement his power with more contact, as his strikeout rate has ballooned from 21.1% in Triple-A to 31.8% in the Majors.
-- Andrew Simon

Jo Adell -- OF, Angels
Key number: 115.5 mph max exit velo

OK, so Adell was bad last year. Really bad. You know who else was bad when he got called up? Mike Trout. We're not saying Adell is Trout -- only Mike Trout is Mike Trout -- but you can forgive a top prospect with tons of talent for struggling at age 21. Now here's one bright spot we saw from Adell in 2020: he can hit the ball hard. Really hard. Like, top-of-the-spectrum exit velocity.

Adell had one of the highest maximum exit velocities of any MLB player in 2020, and he was one of only 15 players to hit a ball in the air at over 115 mph (Adell lined a 115.5 mph single against the Dodgers on Aug. 16). The others? Giancarlo Stanton, Pete Alonso, Rafael Devers, Vladimir Guerrero Jr., Miguel Sanó, Luis Robert, Matt Chapman, Marcell Ozuna, George Springer, Manny Machado, Teoscar Hernández, Ketel Marte, Rowdy Tellez and Gary Sánchez. Hitting the ball that hard is a rare skill. It doesn't guarantee you'll be a great hitter, but it's an indicator that you have a high ceiling. Adell can do something most big leaguers can't. Now he just needs to stop swinging and missing at everything.
-- David Adler

NATIONAL LEAGUE

Dylan Carlson -- OF, Cardinals
Key number: 28.9% hard-hit + sweet-spot rate

Don't let Carlson's slump when he got his first big league callup fool you. There's a reason this kid was hitting cleanup for the Cardinals by the playoffs. Carlson makes great contact. Nearly 30% of his contact was both hard-hit (95+ mph) and in the launch angle sweet spot (8-32 degrees, which covers the line drives that go for base hits and the fly balls that go for home runs). That was a top-five hard-hit/sweet-spot rate in baseball, trailing only Freddie Freeman, Matt Chapman, Will Smith and Corey Seager.

Hitting the ball hard is good. Hitting the ball in the air is good. Hitting the ball hard and in the air is better. Carlson's quality of contact and vast improvement down the stretch and into the postseason gives us plenty of reason to believe in him next year. He's going to be an NL Rookie of the Year contender in 2021.
-- David Adler

Austin Riley -- 3B/LF, Braves
Key number: 23.8% K-rate in 2020

At first glance, it might seem that Riley’s 2020 was a disappointing repeat of his ‘19 debut, which fizzled after an early home run frenzy. In some ways, it was. In the first season, Riley got 297 plate appearances and produced a below-average OPS+ of 86. In the second season, it was 206 plate appearances and an OPS+ of … 86. But bubbling beneath the underwhelming big picture was something encouraging. Riley chased less and made contact more. His walk rate ticked up. And his strikeout rate (36.4% as a rookie) dropped 12.6 percentage points -- the third-largest decrease of anyone with at least 100 PA in both seasons.

That’s a huge development, because when Riley puts the bat on the ball, great things can happen. His 12.0% career barrel rate is excellent. Riley has homered on 8.4% of his career batted balls, on par with Bryce Harper, Juan Soto and teammate Marcell Ozuna since 2019. He can crush the ball 470-plus feet. The caveat here is that Riley’s quality-of-contact numbers all dropped last year, perhaps as a sacrifice to his increased contact. But Riley is just 23, with limited experience, and after a slow start in 2020, he slashed .281/.348/.461 in his final 33 games. This could be the year it all comes together.
-- Andrew Simon

Gavin Lux -- 2B, Dodgers
Key number: Career 20.2% chase rate

A year ago at this time, Lux was the No. 2 prospect in baseball, seemingly set to compete for the starting job at second base with the Dodgers. Los Angeles reportedly refused to include him in trade talks involving Mookie Betts, building their offer around Alex Verdugo instead. But Lux ended up playing just 19 games and logging 69 plate appearances with a .175/.246/.349 slash line and three homers. No longer qualifying as a rookie, Lux has been removed from prospect lists and is something of a forgotten man heading into 2021. Enrique Hernández and Joc Pederson are gone, but the Dodgers’ roster is still among the deepest in the game, leaving Lux with an unclear path to playing time.

Still, his talent shouldn’t be overlooked. This is a player who destroyed Triple-A pitching to the tune of a .392/.478/.719 line with 13 homers over 49 games in 2019. While he has yet to come close to replicating that production in the Majors, at least he hasn’t made a habit of swinging at junk. Lux has recorded a 20.2% chase rate over the past two years, much lower than the MLB-wide chase rate of 28.4% in that span. His hard-hit, sweet-spot and barrel rates are all around the big league average, meanwhile. It’s a solid foundation on which to build.
-- Thomas Harrigan

Ryan McMahon -- 3B, Rockies
Key number: 46.2% hard-hit rate since 2018

After McMahon hit 24 homers in 141 games in 2019, he seemed ripe for a breakout in ‘20. Instead, he took a bit of a step back across the board, slashing .215/.295/.419 in 52 games, with each number lower than his 2019 mark. But there’s evidence that he has the tools to turn that power story back around and continue to improve. He has a 46.2% hard-hit rate since 2018, including a 43% mark in 2020 and 48% in ‘19. Making that kind of contact at Coors Field is bound to help the power numbers.

If anything, it appears that one of McMahon’s issues at the plate last year was a rising strikeout rate -- from 29.7% in 2019, already well above the MLB average, to 34.2% in '20. If he can put the ball in play more, he can capitalize on that power and be a more consistent hitter. He’s been working on adjustments, and it seems like this could be the year it all comes together for McMahon, who is likely to play third base with Nolan Arenado gone.
-- Sarah Langs

Carter Kieboom -- 3B, Nationals
Key number: .287/.378/.469 MiLB slash line

This pick has little to do with Kieboom’s Major League resume, because his early returns haven’t been promising. The Georgia native has hit .181 across his first 165 big league plate appearances, lost playing time to Asdrúbal Cabrera last summer and was optioned to the alternate training site. The Nationals have given their former top prospect ample opportunities to establish himself; he hasn’t done so yet.

So this pick is based more on Kieboom’s track record in the Minors -- including a very strong .303/.409/.493 slash line in 109 Triple A games in 2019 -- and the Nationals’ continuing faith. “I’ve told him, ‘Hey, you’re our future third baseman, and the future is now,’” manager Dave Martinez said of Kieboom back in December, and the fact that Martinez and general manager Mike Rizzo have opted not to make a serious run at upgrading the position (say, by trading for Kris Bryant) hints to me that they also feel Kieboom can rebound.
-- Matt Kelly