Every year offers its share of breakout players, which usually number in the dozens. Most of them reveal themselves right away, at least to the point of answering the ownership question. And then by the end of April, they've graduated from curiosity to full-fledged asset.

Breakouts don't just happen from one season to the next, of course, but in cases where a player finds his footing midstream, suspicions tend to run higher. I don't know if it's because the earliest days of a new season stick out the most, our first impressions becoming emblazoned in our memories, or because both supply of and demand for Fantasy Baseball analysis tends to decline after that first month. But whatever the reason, a delayed breakout can sometimes get lost in the shuffle.

So here are the ones who I think took that step forward in May, raising their stock for the long haul. To be clear, it's not just the players who had a good month but the ones whose good month I'm most confident is a sign of things to come.

1. Lucas Giolito

Lucas Giolito
CHW • SP • 27
ERA2.54
WHIP.95
IP67.1
BB20
K78
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At the end of April, Lucas Giolito had a 5.30 ERA and was sitting out with elbow inflammation. There were signs that maybe his stuff would play better this year, such as an impressive first start against the Royals, but they were overshadowed by all that went wrong thereafter.

Fast forward a month, and he's riding a stretch of five starts in six with at least seven innings and eight strikeouts. Those early signs of improved stuff have been verified several times over. His velocity is up, and his slider and changeup are both playing up, giving him a swinging strike rate that sits among some of the best pitchers in the game. Even the walk rate has come down from those early shaky outings. He has had some home run luck and may not be able to sustain an ERA south of 3.00, but with a workhorse mentality and what's now clearly a swing-and-miss arsenal, he's not someone you'll pay much thought to sitting anymore.

2. Brandon Woodruff

Brandon Woodruff
MIL • SP • 53
ERA3.82
WHIP1.20
IP68.1
BB19
K80
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At the end of April, Brandon Woodruff had a 5.17 ERA and zero quality starts, only once going the minimum six innings required for one. He had well more than a strikeout per inning and was piling them up with reasonable efficiency, having reached the 100-pitch threshold once in six starts, but he wasn't a pitcher anyone was aching to have in his lineup.

Fast forward a month, and Woodruff is up to four quality starts, including two of the eight-inning variety. He has remained ultra efficient, now only twice reaching the 100-pitch threshold in 12 starts despite a workhorse build and a varied enough arsenal (four pitches in all, including three with at least decent swing-and-miss potential) to allow him to go deep into games. His fastball in particular looks like an overpowering pitch, prompting Bryce Harper to compare him to "Matt Harvey when he came up." True, Woodruff kicked off June with a stinker, but it's forgivable now that we have a clearer idea what the 26-year-old's ceiling is.

3. Rafael Devers

Rafael Devers
BOS • 3B • 11
BA0.316
HR8
SB7
OPS.870
AB225
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At the end of April, Rafael Devers had zero home runs and a fly-ball rate so embarrassingly low that you had to wonder if he'd ever hit one. His strikeout and walk rates were both the best they'd ever been, but in an era where everybody who's anybody hits for power, it was merely a footnote for what seemed like a top prospect gone bad.

Fast forward a month, and he's up to eight home runs. The strikeout and walk rates (particularly the former) are still the best they've ever been, but now he's back to elevating the ball like he did earlier in his career. His breakthrough didn't come in the most conventional manner, but it came all the same for a player whose 22 years of age probably should have earned him more benefit of the doubt. Even his high BABIP isn't real cause for concern given his high line-drive rate and willingness to hit the ball the opposite way.

4. Frankie Montas

Frankie Montas
OAK • SP • 47
ERA2.81
WHIP1.20
IP64.0
BB18
K66
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At the end of April, Montas had less than a strikeout per inning and nearly a hit per inning. There was talk of a new split-finger fastball being the swing-and-miss pitch he had long lacked, but his swinging strike rate still ranked in the lower third of the league. His 3.99 FIP suggested that whatever success he was having would soon come crashing down, as happened after a hot start last year.

Fast forward a month, and that FIP is now 2.88. The splitter has proven to be a legitimate swing-and-miss offering and has helped make his 99 mph fastball one, too. His swinging strike rate now ranks among the upper half of the league, and the one he put together in May would rank in the top 20. Better yet, he has emerged as a top-10 ground-ball pitcher, which should do as much to keep his ERA down as the improved strikeout rate will. 

5. Ketel Marte

Ketel Marte
ARI • CF • 4
BA0.280
HR14
SB3
OPS.865
AB236
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At the end of April, Ketel Marte was batting only .250, and it wasn't clear at that point if his newfound power was to blame. His fly-ball rate was way up, which can be a BABIP killer, and though it had translated to seven home runs so far, it wasn't clear such power was even within his skill set, not a guy whose career high in home runs was only 14.

Fast forward a month, and he's one home run away from that career high. His batting average is up 30 points, actually higher than it was last year, and his BABIP suggests there's nothing illegitimate about it. In fact, his entire batted ball profile looks close to what it was a year ago except in the ways that would make him an obvious beneficiary of what's become an even more homer-friendly environment, his home run-to-fly ball rate being double what it was a year ago. It's not an outrageous number for someone hitting the ball as hard as he has, though, which explains why his wOBA and xwOBA line up, and after two months with basically the same home run total, there's even more reason to believe the power will continue.

6. Gleyber Torres

Gleyber Torres
NYY • SS • 25
BA0.293
HR14
SB3
OPS.879
AB215
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At the end of April, Torres had only a .768 OPS despite a normal BABIP, a normal strikeout rate and a normal home run-to-fly ball rate. It was seemingly validation that his successful rookie season was mostly a product of an early home run binge, leaving a pretty ordinary player in its wake.

Fast forward a month, and Torres now has an .879 OPS despite his BABIP, strikeout rate, and home run-to-fly ball rate all still looking ... pretty normal. Neat trick, huh? Partly, it's because "normal" takes on a different meaning for a player with only one year of major-league experience. The strikeout rate and home run-to-fly ball rate are both better than they were a year ago, but not in a way that would raise suspicions. And there's an internal consistency to the numbers that suggests Torres hasn't played over his head. They're the sort of across-the-board improvements you'd expect for a top prospect in his second year, and while each is small on its own, they're adding up to something big.