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Five hot fantasy baseball waiver wire pickups, streamers, and sleepers for Week 1 (2026). Undervalued hitters outperforming their ownership percentage and should be more widely owned.
With the first "week" of MLB action in the books, the waiver wire is beginning to take shape, and managers are starting to spot the weakness on their roster. In this weekly piece, I will suggest five "bargain" hitters to pick up off the wire who are rostered in less than 25% of current Yahoo leagues.
This week, we will look at a few post-hype hitters who may be taking their game to the next level and two young hitters who have carved out early full-time roles on their respective rosters.
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Colt Keith, 2B/3B, Detroit Tigers
18% rostered (Yahoo)
Colt Keith was a former highly regarded prospect in the Detroit system, but has yet to reach "star" status in fantasy baseball. In 2024, Keith made his MLB debut and spent 146 games with the Tigers. During this stint, Keith held a .260/.309/.380 line with a low .689 OPS.
The following season, the young infielder took some strides forward, posting a .256/.333/.413 slash line with a .746 OPS. While he hit the same total of home runs (13), he hit 22 doubles (an increase from 15) and showed positive progress under the hood.
In 2025, Keith raised his hard-hit rate to 43.7%, a nice jump from the 35.3% he held as a rookie, which placed him just above the average marks. Additionally, Keith posted a 71st-percentile .341 xwOBA, .257 xBA, and .444 xSLG, suggesting there was even more room for growth as he entered his third full MLB season.
The 24-year-old has not only taken another step forward in the early part of 2026, but is performing as one of the top hitters in the sport. In a short five-game sample, Keith has gone 7-for-18 with three doubles, two RBI, four runs, and a 6:2 K:BB. While the sample is small, Keith has continued to make steady strides and should be a top target on the waiver wire this week.
First, Keith has continued to show an impressive eye at the plate, especially when drawing walks. Through the early going in 2026, Keith has posted a 12.5% BB%, a nice jump from the 10% he led the year prior and the low 6.5% BB% he posted as a rookie. Additionally, Keith has also begun to pull the ball at a much higher rate.
Given that there has only been a week of games, Keith sits with an incredible 30.0% Pull AIR%, which is sure to normalize over the summer. However, even if it were to drop, this would still be a massive increase over the 18.0% Pull AIR% he held in 2025. If he can continue to pull the ball effectively, his power numbers will be rewarded.
He has also posted a low 30.0% ground-ball rate, which is on pace for an eight-point drop compared to 2025. While he will continue to sit against left-handed pitchers, the Tigers recently bumped him up to the leadoff spot against right-handed starters on Tuesday night, suggesting they not only trust him to spark the offense but will also continue to put him in prime scoring situations.
The young infielder has also raised his bat speed to 73.5 mph, which is on pace to be the highest of his career.
AJ Hinch hinted at Colt Keith moving up in the order last night: "I want him up to bat a lot. He controls his at-bats, he's walking, he's hitting the ball hard...he's a real offensive threat."
--Carpenter's 10-K start wasn't going to keep him at the top of the order for long.— Chris McCosky (@cmccosky) March 31, 2026
Given his multi-positional eligibility on Yahoo (and most other platforms), Keith is worth picking up in all leagues ahead of Week 2. If he can maintain these higher pull rates, the home run production will come.
Owen Caissie, OF, Miami Marlins
19% rostered
Owen Caissie was the centerpiece in one of the major trades this offseason as he was shipped from the Chicago Cubs to the Miami Marlins. In return, the Cubs received right-handed pitcher Edward Cabrera. Caissie is currently listed as MLB.com's No. 42-ranked prospect, as he flashed immense upside in the upper minor leagues ahead of his MLB debut.
In 2025, Caissie logged 99 games with the Iowa Cubs and held a .286/.386/.551 line with 28 doubles, 22 home runs, five stolen bases, and an impressive .937 OPS. While he struck out at a 27.9% rate, the power upside he flashed made him a top stash candidate to take over the season. He would eventually make his debut with the Cubs in the second half of the season and post a modest .192/.222/.346 line with one home run over a 12-game stint.
However, joining the Marlins, Caissie was immediately given a full-time role. Despite a rough showing in spring training, Caissie opened the season as the primary right fielder against right-handed pitching. Over his first two games, Caissie would go 4-for-8 with a stolen base. In his third game, he would start the day on the bench but would hit the game-winning walk-off home run as a substitute.
OWEN CAISSIE WALK-OFF TWO-RUN HOMER 🤯 pic.twitter.com/bz3QkvlvqI
— MLB (@MLB) March 29, 2026
Overall, through seven games, he has gone 6-for-15 with a long ball, two doubles, and a stolen base.
In this early stint, Caissie has lowered his strikeout rate to 21.7%, a very promising sign, as it was one of his primary flaws as a prospect. He is also hitting the ball very hard (50.0% hard-hit rate) and pulling the ball at a 20.0% Pull AIR%.
While the high whiff concerns could show again and lower his value in points leagues, he possesses 20+ HR upside and should be rostered in all five-outfielder leagues.
TJ Rumfield, 1B, Colorado Rockies
5% rostered
The Rockies' first base job was not a highly watched competition during spring training. TJ Rumfield competed alongside No. 3 overall pick Charlie Condon and Edouard Julien. In camp, Rumfield ran away with the job, despite not taking a single previous MLB at-bat, as he posted an impressive .286/.359/.554 line with a .913 OPS and five home runs over a 23-game stint.
The 25-year-old has picked up right where he left off in spring training and has enjoyed a hot start to his MLB career. Over his first five games in Colorado, Rumfield has tallied eight hits with two of them going for extra bases (one home run) and holding a 5:2 K:BB.
The 25-year-old has continued to hit in the heart of the lineup (in the five-hole), while he has provided prime RBI opportunities, despite batting in one of the game's worst lineups. While his MLB track record is very short, Rumfield has generated an elite 50.0% LA Sweet-Spot% with a 20.0% Pull AIR%, which are very promising underlying marks. He has also posted a 40.0% hard-hit rate with an above-average 10.0% barrel rate.
Through 252 career games at Triple-A (in the Yankees system), Rumfield was very productive, holding a .288/.372/.453 line with 31 long balls and an .825 OPS. Even though his track record is not lengthy and his overall counting stats that will likely remain the lowest on this list, Rumfield possesses near 15+ HR upside in calling Coors Field home.
He is worth adding in deeper leagues as an upside corner infielder.
Cole Young, 2B, Seattle Mariners
9% rostered
There may not be a player who increased his fantasy stock more in the spring on this list than Cole Young. After posting a modest .211/.302/.305 line with just four home runs over his first 77 MLB games last season, the 22-year-old has taken a major step forward following a full offseason.
In camp, the former 21st overall pick posted a .281/.349/.667 line with four doubles, six home runs, and three stolen bases over a 19-game stint. Before reaching the majors in 2025, Young showcased a similar five-category skill set at Triple-A, hitting five home runs with four stolen bases over a 54-game stint.
Seeing Young begin to tap into this profile was a very positive sign and made him a sneaky late-round sleeper in deeper 15+ team leagues in the spring. Fortunately, the young infielder has continued this trajectory and is quickly establishing himself as a viable starter in all standard leagues.
Through six games, Young has held a .333/.364/.571 line with two doubles and one home run. Since going hitless on Opening Day, Young has tallied at least one hit in each of his last five games while holding a 1.088 OPS.
While the stolen bases have yet to show this season, he currently sits with an above-average sprint speed, and better days are ahead. Young has a 15/15 profile and should remain the everyday second baseman in Seattle, given his current production. While his seat may get warm if top prospect Colt Emerson knocks on the MLB door, for now, this is Young's job to lose.
Miguel Vargas, 1B/3B, Chicago White Sox
18% rostered
Rounding out the first edition of this piece will be one of the most surprising breakouts of the first week: Miguel Vargas. Vargas was a former top prospect in the Dodgers system, but was never given a full opportunity to find his footing in Los Angeles. He was eventually moved to Chicago as part of the Michael Kopech trade and has since found an everyday role in the offense.
In 2025, Vargas strung together a solid campaign during his first "full" taste of the majors. Over a career-high 138 games, Vargas posted a .234/.316/.401 line with 32 doubles, 16 home runs, and six stolen bases. He scored 80 runs and took on 60 RBI while batting in a young Chicago lineup.
Under the hood, he generated a promising 36.6% LA Sweet-Spot% while showing an above-average eye at the plate, drawing walks at a 9.8% rate and striking out at a 17.6% rate.
He entered the 2026 season as a primarily "points league option" given his eye, but has since emerged as a viable starting option across all formats. Through five games, Vargas has hit one home run (including a grand slam), swiped one bag, and held a strong .294 AVG.
Miguel Vargas with an absolute nuke. His grand slam gives Chicago an 8-0 lead.
Rough debut for Paddack, who looked sharp early on. pic.twitter.com/tJvovxsW7S
— Isaac Azout (@IsaacAzout) March 30, 2026
During this short taste, he has generated a remarkable 33.3% Pull AIR%, which is a 10-point jump from 2025. A major increase in this could significantly raise his power output over the summer.
Additionally, the White Sox have already begun playing Vargas at multiple positions (first and third base), suggesting they will look to find opportunities for him in the starting nine. He is a top target ahead of Week 2 and is worth trusting as a starting corner infielder/utility bat in all formats ahead of a potential post-hype breakout campaign.
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