Marcelo Mayer, Jac Caglianone Among American League Fantasy Baseball Sleepers

A breakdown of the top American League fantasy baseball sleepers for 2026, featuring breakout hitters, rebound pitchers, and prospects ready to outperform their ADP.

Kansas City Royals right fielder Jac Caglianone (14) hits a home run during the seventh inning against the Toronto Blue Jays at Kauffman Stadium. | Jay Biggerstaff-Imagn Images

Identifying American League sleepers is one of the most effective ways to gain an edge in 2026 fantasy baseball drafts. From rising prospects like Samuel Basallo and Jac Caglianone to post-hype breakout candidates such as Jasson Domínguez, these under-the-radar players could deliver massive value relative to their current draft cost.

Jack Perkins, Athletics

Three games into spring training, Perkins appears to have pitched his way out of a starting job after allowing four runs, six hits, a home run, five walks, and four strikeouts over 5.1 innings. The A’s gave him 12 games of experience last season (3-2 with a 4.19 ERA, 1.164 WHIP, and 37 strikeouts over 38.2 innings), where his arm showed flashes of upside. He pitched much better over his nine starts at AAA (2.86 ERA, 1.023 WHIP, and 68 strikeouts over 44.0 innings) despite walking 4.1 batters per nine.

In 2024, Perkins was treading high at AA (4-1 with a 2.96 ERA, 1.145 WHIP, and 103 strikeouts over 78.0 innings).

I have Perkins listed as a sleeper, as he may emerge as the A’s top closing option. Walks have been a problem in his pro career (3.9 per nine in the minors and 4.2 last year in the majors) while being even worse over three seasons at Indiana (6.0). He brings strikeout ability to the Athletics’ bullpen, and a shorter rotation of pitchers could lead to fewer free passes late in games. Perkins had a live fastball (96+ mph), supported by a swing-and-miss slider. 

Samuel Basallo, Baltimore Orioles

Baltimore Orioles catcher Samuel Basallo (29) runs off of the field during the sixth inning against the New York Yankees at Oriole Park at Camden Yards. | Daniel Kucin Jr.-Imagn Images

At age 21, Basallo looks poised to have a season-long opportunity in the majors. His future isn’t at catcher, suggesting a rotational role this year between catcher, first base, and DH. His bat brings 30+ home run upside out of the gate, but Baltimore may only give him 450 at-bats. Basallo should chip in with some steals while on a path to deliver a neutral batting average. Right kind of upside swing in 2026.

This spring, Basallo has six hits over his first 18 at-bats with five runs, two RBIs, while taking four walks and striking out five times.

Marcelo Mayer, Boston Red Sox

Mayer is competing with Caleb Durbin, Romy Gonzalez, and Kristian Campbell for playing time at second and third base. Boston locked up Campbell in 2024 for $60 million for eight seasons, suggesting a better opportunity this year. 

Mayer has a high enough average hit rate (1.747) to produce over 25 home runs if given 550 at-bats, which may be a lot to ask based on his low experience at AAA (.271/31/9/43/2 over 170 at-bats). He also offers sneaky speed. For now, Mayer sits in a cloudy situation, while having an injury risk on his profile.

His bat has been quiet so far in spring training (3-for-13 with two runs, one home run, and one RBI with three walks and three strikeouts).

Miguel Vargas, Chicago White Sox

Last season, Vargas finished 133rd in FPGscore (-2.24) for hitters while missing 14.8% of the season. Based on his home run/barrel ratio (42.1%), he ranked (12th) near the bottom of the league in this area (minimum of 30 barrels). The league average is about 48.0%. He is the 179th batter drafted this year in mid-February.

Vargas brings a flyball swing path with a winning contact rate (83.4%). I expect a massive uptick in his contact batting average, making him one of the better deep-sleeper breakout hitters in 2026. Last year, the White Sox gave Vargas 82.3% of his at-bats in the top four slots in the batting order, showcasing his favorable opportunity. With a healthy season and 550+ at-bats, I expect a push over .270 in batting average with 90 runs, 25 home runs, 85 RBIs, and 10+ steals.

Parker Messick, Cleveland Guardians

Cleveland Guardians starting pitcher Parker Messick (77) throws to the Minnesota Twins in the first inning at Target Field. | Bruce Kluckhohn-Imagn Images

For fantasy teams looking for backend strikeouts, Messick fits the bill. He was too hittable in his short stint with Cleveland last year, highlighted by his batting average against (.289 BAA). His changeup sets the tone for his ceiling, which will also be helped by better overall command. 

Messick looks poised to make 30 starts in the majors this year. I view his profile similarly to Andrew Abbott, but with better foundational skills. His build (6’0” and 225 lbs.) suggests an underlying workhorse arm once he gains more experience. In my thoughts, with a chance at 175+ strikeouts with about a 3.60 ERA and 1.200 WHIP.

Over his three appearances this spring, Messick allowed two runs and 10 baserunners over 9.1 innings with seven strikeouts. 

Kevin McGonigle, Detroit Tigers

The Tigers should start McGonigle at AAA while trying to project another year of service. His ability to take walks and put the ball in play puts him on the fast track to the majors. The growth of his swing path in 2025 suggests his whole package is coming quicker than expected. McGonigle’s next step is adding more length to his season (never had over 400 plate appearances in his career). 

He falls into the upside stash category in deeper formats. The high-stakes market in mid-February believes McGonigle is worthy of backend middle infield investment. Player to watch this spring, while projecting well as a stash in AL-only formats.

McGonigle looks poised to break camp with the Tigers after opening spring training with seven hits over 20 at-bats with six runs, one home run, two RBIs, and one steal. His ADP moved into the 17th round in the high-stakes market (15-team format) on Monday night (3/9).

Cristian Javier, Houston Astros

When at his best for Houston in 2021 and 2022, Javier allowed only 156 hits over 250.0 innings, showcasing his elite arsenal (2.95 ERA, 1.044 WHIP, and 324 strikeouts) despite walking 3.8 batters per nine innings.

Since his TJ surgery in June of 2024, he’s only pitched 37 innings for the Astros (2-4 with a 4.62 ERA, 1.270 WHIP, and 34 strikeouts), with crook stats in the minors (10 hits, 15 walks, and 15 strikeouts over 14.0 innings with 15 strikeouts).

In an exhibition game on March 3rd, Javier allowed one run and three hits over two innings with no walks or strikeouts. His fastball peaked at 93.9 mph. If his command returns to at least his previous form, he has the tools to be a helpful backend arm due to the low number of hits allowed. A spring follow is a must, as Javier should be much improved this year.

His right arm was off in his only spring training appearance (one run, one hit, three walks, and three strikeouts over 1.2 innings).

Jac Caglianone, Kansas City Royals

Caglianone is a future power beast who comes into this year with plenty of questions for fantasy drafters. His lack of success in 2025 suggests there is work to be done. A .209 contact batting average is so far below what is expected from a major league bat, and his 2025 minor league season (.430).

Caglianone looked major league ready last year when he blasted his way through AA (.322/32/9/43/2 over 152 at-bats) and AAA (.357/26/11/29/1 over 112 at-bats). His strikeout rate (18.8%) was favorable while taking plenty of walks (10.2%).

The dance with his bat is about upside, and Caglianone will soon be a top 20 major league bat. He falls into the category of a breakout hitter of the year, and his bat has been trending favorably this spring (6-for-15 with six runs, one home run, and four RBIs while taking five walks and striking out three times). His ADP in the NFBC moved to 157 in 15-team formats.

Reid Detmers, Los Angeles Angels

For the fantasy drafters chasing Detmers’ ceiling around for five seasons, they have paid off only once (2022 – 7-6 with a 3.77 ERA, 1.209 WHIP, and 122 strikeouts over 129.0 innings). The Angels downgraded him to a bullpen arm for all of last season, leading to minimal growth based on his final surface stats (3.96 ERA, 1.304 WHIP, and 80 strikeouts over 63.2 innings).

Over his final 46 games in 2025, Detmers arrived as a trusted major league arm (2.18 ERA, 1.059 WHIP, and 61 strikeouts over 45.1 innings). His strikeout rate (12.1) was elite over this span, with some progress in his command (3.2 walks per nine).

Detmers moved to the 21st round of the NFBC main event draft season, despite losing results in spring training (seven runs, 15 baserunners, and eight strikeouts over 8.2 innings). He falls into the deep flier category with the talent to be a much better arm if Detmers returns to the starting rotation. 

Mick Abel, Minnesota Twins

Minnesota Twins pitcher Mick Abel (20) pitches during the third inning against the Detroit Tigers at Publix Field at Joker Marchant Stadium. | Mike Watters-Imagn Images

Over three appearances this spring, Abel has been dominate in each outing, leading to 10.0 shutout innings with five hits, no walks, and 13 strikeouts. His arm showed growth last season at AAA (7-2 with a 2.20 ERA, 1.108 WHIP, and 114 strikeouts over 98.0 innings), but major league bats beat him up (27 runs, 59 baserunners, and eight home runs over 39.0 innings with 39 strikeouts). His stock has been flying up draft boards in early March.

Jasson Dominguez, New York Yankees

With Cody Bellinger added to the Yankees’ outfield, playing time gets cloudier for Dominguez this year. He must outplay Trent Grisham to earn a full-time starting job unless Giancarlo Stanton lands on the injury list. For now, I view him as a 20/30 player with batting average risk once given at least 500 at-bats. 

He looked overpriced in late January, but Dominguez has slipped in drafts (ADP – 347) even with Stanton batting elbow issues in early March. Over his first nine games in spring training, he went 8-for-27 with five runs, one home run, seven RBIs, and one steal, but he did whiff nine times. 

Kade Anderson, Seattle Mariners

If Bryce Miller isn’t ready to go on opening day, Anderson will try his best to jump Emerson Hancock on the Mariners’ pitching depth chart. Seattle drafted him third overall in the 2025 MLB June Amateur Draft after showing growth in his final season at LSU (12-1 with a 3.18 ERA, 1.059 WHIP, and 180 strikeouts over 119.0 innings). Anderson allowed two runs and five baserunners over five innings in two games this spring. He’ll turn 21 in July with no experience in the minors.

Ian Seymour, Tampa Bay Rays

Seymour brings craftiness to the pitching mound that frustrates batters due to his ability to change speeds. He averaged 11.0 strikeouts per nine innings in the minors with reasonable command. Over 28 games at AAA, he went 14-4 with a 2.34 ERA, 1.120 WHIP, and 176 strikeouts over 150.00 innings. 

He pitched 145.1 innings in 2024 and 143.0 last season, putting Seymour on a path to make 30 starts for Tampa this year. I like the sum of his parts, and I expect him to outperform his ADP. Think double-digit wins with a sub-3.50 ERA and a run at 175 strikeouts. He’ll have some down days, but the good should outweigh the bad by a wide margin.

Seymour pitched well over his first three spring training games (three runs, nine baserunners, and eight strikeouts over 7.2 innings), but he has slid in high-stakes drafts (ADP – 343).

Evan Carter, Texas Rangers

Texas Rangers center fielder Evan Carter (32) in the dugout after scoring a run in the eighth inning against the Los Angeles Angels at Angel Stadium. | Jayne Kamin-Oncea-Imagn Images

Based on the Rangers’ roster in mid-February, Carter looks poised to bat leadoff this season despite only having 23 career at-bats in the first and second spots in Texas’s batting order. He has struggled so far against lefties (.083/8/0/3 over 60 at-bats) while striking out 30.9% of the time, suggesting a potential platoon role. Carter has gone homerless over his last 178 at-bats vs. left-handed pitching.

If health concerned was removed from his outlook, Carter has the talent to be a 20/30 player with a chance to score over 100 runs and drive in 70 RBIs. His batting average should also be an asset. His lower price point takes out much of the investment cost and injury risk. There are many hurdles to clear, but he has the talent to be a difference-maker this year if Carter stays upright for 500 at-bats.

Over his first nine games in spring training, Carter went five for 20 with three runs, two home runs, five RBIs, and one steal while taking four walks and striking out seven times. His ADP (291) sits in the 20th round of 15-team drafts.

Kazuma Okamoto, Toronto Blue Jays

Toronto should hit Okamoto one slot off Vladimir Guerrero, helping his runs or RBIs. There will be a learning curve in the majors, but he still should have a chance to deliver a neutral batting average with an 80/25/80 profile. My mental picture is of a slightly better player than Isaac Paredes in offensive production.

Okamoto only has one hit over 10 at-bats with an RBI and two walks in the WBC. He played better to open spring training with the Blue Jays (3-for-9 with three runs, one home run, and five RBIs). His ADP (223) has climbed about 30 picks over the past couple of weeks.

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Fantasy championships are often decided by the players who outperform expectations, and this group of American League sleepers offers plenty of upside at a discount. Whether you’re targeting high-ceiling prospects like Kevin McGonigle or rebound arms such as Reid Detmers, keeping these names on your radar could pay off big during the 2026 fantasy season.