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Five fantasy baseball waiver wire pickups, sleepers, and trade targets for Week 12 -- undervalued hitters outperforming their rostership and should be more widely owned.
As we hit Week 12 of the fantasy baseball season, savvy managers know it’s the perfect time to find value where others aren’t looking.
This week, five hitters -- Willi Castro, Josh Smith, Miguel Vargas, Ryan McMahon, and Sal Frelick -- stand out as underrated assets with the potential to make a real impact.
From positional versatility to hot streaks and expanded roles, these players offer sneaky upside that could help you gain an edge heading into the heart of the summer grind.
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Willi Castro, 2B/3B/SS/OF, Minnesota Twins
57% rostered
A productive 96 first-half games in 2024 that saw Castro bat .265/.352/.422 with 34 extra-base hits resulted in his first All-Star Game appearance. While the 28-year-old wasn't able to maintain that pace in the second half, he has resembled his All-Star form during the first half of 2025, hitting .283 with an .830 OPS in 201 plate appearances, alongside 11 doubles, seven home runs, 17 RBI, 17 walks, and 50 strikeouts in 52 games.
Willi Castro since returning from the IL:
113 PA
.316 AVG
.407 OBP
.531 SLG
.938 OPS
.214 ISO pic.twitter.com/w3YuhHMOUK— Kirk Snyder (@dynastyinfo411) June 13, 2025
Castro was placed on the injured list April 24 with an oblique strain, but has been the Twins' hottest hitter since returning on May 5. He's also slashed .370/.393/.630 over his last seven games, but unfortunately, Minnesota is 2-8 in its last 10.
When Castro gets going offensively, he looks like one of the most underrated hitters in the league. But his strikeout and walk percentages are around the league average, and as we saw last season, Castro wasn't able to keep his momentum in the second half.
His current pace likely isn't sustainable, but he's able to play all around the diamond and in the outfield, offering positional flexibility and offensive upside to your fantasy lineup. Rostering him at least until the end of June may be worth it.
Josh Smith, 1B/3B/SS/OF, Texas Rangers
52% rostered
Smith impressed while filling in for an injured Josh Jung in 2024, earning the first Silver Slugger Award of his career and forcing the Rangers to get him into more games in 2025. The 27-year-old has notched 11 doubles, seven home runs, 20 RBI, 23 walks, and eight stolen bases across 245 PA in 63 games this season.
Smitty sets the tone. 😤
Josh Smith is your AL Player of the Week! #AllForTX pic.twitter.com/wSCIZIXPOz
— Texas Rangers (@Rangers) June 16, 2025
He was especially effective last week, when he slashed .423/.500/.796, earning him American League Player of the Week honors. This performance brought Smith's season average up to .288 and OPS to .800, which both lead the team. The versatile infielder's play this year has him on his way to his first All-Star Game appearance.
Smith's ability to make consistent contact, walk more (9.4%) than the league average (8.5%), and keep his strikeout rate down (17.6% compared to a 22.5% MLB average) has made him the catalyst of the Rangers offense. While his 88.5 exit velocity ranks in the 27th percentile in the league, his .329 BABIP isn't concerningly high, meaning he's not just lucking into his 60+ hits.
Miguel Vargas, 1B/3B/OF, Chicago White Sox
41% rostered
Vargas appeared on this list in Week 8, and we addressed how, in mid-May, the 25-year-old made adjustments at the plate that resulted in increased production and harder-hit balls.
Since we last checked in on him, he's posted an .810 OPS with 14 XBH, 12 RBI, 10 walks, and just 19 strikeouts across 111 PA in 27 games. His totals for the 2025 season are now at .242/.322/.440 with 18 doubles, 10 homers, 31 RBI, 27 walks, and 49 strikeouts in 69 contests.
Miguel Vargas, the best power hitter in Chicago, isn't ready to quit just yet!pic.twitter.com/zh1ss49SZ8
— Just Another Year: White Sox (@JAYChi_WhiteSox) June 15, 2025
He's been hot in his last seven games, too, batting .286/.333/.607. It's not a stretch to say that Vargas has been the best, most consistent hitter on the White Sox this year, still leading the club in multiple offensive categories.
There's always room for improvement in one's game, but Vargas is slowly putting it all together at the major league level. The former Dodger could be on his way to his first ASG appearance and would be a welcome addition to any fantasy team in need of a corner infielder or outfielder.
Ryan McMahon, 3B, Colorado Rockies
32% rostered
Former All-Star and top trade candidate Ryan McMahon is attempting to salvage his season during his ninth year with the Rockies. Now 30 years old, he's slashed .280/.379/.720 with three home runs, five RBI, and four walks in his last seven games. McMahon's recent hot streak has helped boost his season stats to .222/.333/.411 alongside 24 XBH in 71 games.
Although he ranks in the 93rd percentile in walk percentage, with 41 walks in 291 plate appearances, McMahon still strikes out a lot, with an uninspiring 35.1% Whiff% and 30.1% K%. That said, playing in Coors Field makes him prone to more homers, and he's had five in 15 games this month -- including three on the road. McMahon is on the upswing.
Taco's Tuesday 🌮 pic.twitter.com/50o9p5fI2s
— Colorado Rockies (@Rockies) June 18, 2025
Perhaps the lefty hitter, who hit 119 homers from 2019-24, is trying to increase his trade value. McMahon has been floated as a potential trade candidate for a few seasons now, but Colorado has failed to deal him.
He signed a six-year contract extension in 2022, which means he will not become a free agent until 2028. We've seen how this fleshed out before for the Rockies, so McMahon will likely still be playing his home games in Denver until further notice.
Sal Frelick, OF, Milwaukee Brewers
31% rostered
It's the "Summer of Sal," as 2021 first-round pick Frelick is off to one of the best first halves of his young career in 2025. He's posted a .289/.350/.391 slash line with eight doubles, three triples, four home runs, 26 RBI, and 21 walks across 282 PA. His batting average, on-base percentage, and OPS all lead the team.
Most recently, he's slashed .296/.345/.370 in his last seven games, looking every bit like the player he was touted to be as a former first-rounder out of Boston College. The 2024 Gold Glove Award winner boasts stellar plate discipline and pitch selection, placing in the 92nd and 98th percentiles in Whiff% and K%, respectively.
Frelick also possesses tremendous speed, with his 14 stolen bases (2 CS) ranking second on the team, behind only Brice Turang.
Lighting up the base paths @SalFrelick x @Bryanchourio11 pic.twitter.com/540cP0jqKg
— Milwaukee Brewers (@Brewers) June 14, 2025
He has all of the tools to be a successful big leaguer for years to come. But for now, Frelick can help your fantasy team amid his hot streak by providing XBH and stolen bases.
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