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Are Seth Halvorsen, Otto Lopez, Kristian Campbell fantasy baseball sleepers, busts, or neither? Rick takes a deep dive into their 2025 fantasy baseball values.
The 2025 fantasy baseball season is officially underway, and that means another season of Champ or Chump. This column is a deep dive into one to three players per week, looking at prospect pedigree, MiLB performance, Statcast data, role, peripherals, team context, and more. At the end of our analysis, we determine whether each player is a Champ or Chump relative to their roster rate on Yahoo! leagues.
It's easy to overreact to the first handful of games, but Rafael Devers probably won't be the worst player in baseball this year. Still, now is the best time to find a waiver wire gem since you can roster them for nearly the entire season.
Three of the more intriguing names thus far are Seth Halvorsen, Otto Lopez, and Kristian Campbell. Let's find out if they're fantasy mainstays or flashes in the pan!
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Seth Halvorsen, RP, Colorado Rockies
19% Rostered
Halvorsen introduced himself to the fantasy world by notching a save on March 29, immediately attracting attention since we're always looking for saves. His team isn't very good and Coors Field is a hitter's paradise, but Halvorsen has a shot to run with Colorado's closer job.
Fantasy managers need strikeouts from their relievers, and Halvorsen should deliver. He pitched six innings at Double-A (Hartford) in 2023 but really reached the level last season, posting a 4.84 ERA but 3.89 xFIP in 35.1 innings. His 25.9 percent K% was solid, though he walked a few too many with a 12 percent BB%.
The performance earned him a trip to Triple-A (Albuquerque) where he only logged nine innings. He was absolutely dominant with a 39.5 percent K% and 10.5 percent BB%, logging a 3.00 ERA and 2.64 xFIP in the notorious Pacific Coast League.
The Rockies were so impressed they called him up to the Show, and he was fantastic with a 1.46 ERA and 3.50 xFIP in 12.1 IP. His 28.8 percent K% and 4.3 percent BB% were outstanding, and he averaged 99.9 mph on the radar gun with a max velocity of 102.5 mph.
It was a small sample size, but you cannot fake great stuff. Halvorsen's fastball generated a 10.6 percent SwStr% and 56.1 percent Zone%, while his split acted as a second fastball with a 16 percent SwStr% and 54.7 percent Zone%. His sinker generated a 67.6 percent Zone% but little else with a 5.9 percent SwStr% and 33 percent ground ball rate.
Halvorsen's slider proved to be his best pitch with a 25 percent SwStr%, 40 percent chase rate, and 46.4 percent Zone%. It was the fourth pitch in his arsenal last season but his most-used offering in his four-out save against Tampa Bay, suggesting he might throw it more this season. That could easily send his K% above 30 percent.
Fantasy managers also like closers with job security, and the 25-year-old rookie might have it. Colorado's other leverage arms include Victor Vodnik and Tyler Kinley, neither of whom look like closer candidates.
Vodnik logged 73.2 IP last season with a 4.28 ERA, 4.87 xERA, 20.3 percent K%, and 11.6 percent BB%. Those are the numbers of a bulk reliever who comes in to chomp innings in blowout games, something the Rockies figure to have a lot of. It's not ninth-inning material.
Kinley is a 34-year-old with a career ERA of 5.10, a career K% of 23.6 percent, and a career BB% of 11.3 percent. With no upside and little production to speak of, he's more of a DFA candidate than a closer candidate.
The door appears wide open for Halvorsen to establish himself as a solid closer in his rookie year, making him a Champ.
Otto Lopez, SS/2B, Miami Marlins
30% Rostered
Lopez is hitting .333/.444/.533 with a homer and a steal in 18 plate appearances, and he would be great if he could keep that up all season. Spoiler alert: he can't.
Lopez spent most of 2024 on the Miami roster, hitting .270/.313/.377 with six homers and 20 steals in 434 PAs. He's fast with a 28.7 ft./sec Statcast Sprint speed and was successful on 83 percent of his SB attempts, so he'll probably steal about 20 bags again. However, he never stole more than 22 in a MiLB campaign, capping his upside in the category.
Furthermore, Lopez doesn't project for any power. His 25.2 percent FB% was very low, and he didn't do much with the flies he hit thanks to a 7.1 percent HR/FB. He maxed out at five homers as a minor leaguer, so even last year's modest power production appears bound for negative regression.
Lopez doesn't walk (5.8 percent BB%) or strikeout (17.3 percent K%) very often, so his batting average is determined by his BABIP. Last season's .318 BABIP is probably sustainable as a fast guy who doesn't hit many flies, so his average will probably land around .270 again.
Lopez hit second twice and fifth twice so far in 2025. Miami's lineup won't provide many counting stats either way, but his fantasy profile looks better if he solidifies the second spot since he would get a few more runs scored.
Lopez won't actively hurt you, but he won't make a difference in any specific category either. He provides solid value in deep leagues where volume plays, but do 30 percent of Yahoo! leagues fit that criterion? Probably not, so Lopez is a Chump.
Kristian Campbell, 2B, Boston Red Sox
46% Rostered
Campbell is slashing .429/.500/.786 with a homer in 16 PAs as a 22-year-old. He has a solid prospect pedigree as the seventh-ranked prospect in all of MLB per FanGraphs, but immediate success wasn't guaranteed since he has little track record.
Campbell was a bat-on-ball guy in college with little power or baserunning prowess but adjusted his swing as a pro to trade some contact for pop. Scouts loved the results as evidenced by his MLB Pipeline scouting report:
Campbell's swing change translated to MiLB production as well. He hit .362/.463/.582 with eight homers and 17 steals in 255 PAs for Double-A (Portland) last season. His .411 BABIP was obviously unsustainable, but his 13.7 percent BB% nearly matched his 14.9 percent K%. He was also successful on roughly 77 percent of his SB attempts.
The performance earned Campbell a shot at Triple-A (Worcester) where he hit .286/.412/.486 with four homers and steals in 85 PAs. His .333 BABIP was more realistic, and his plate discipline remained outstanding with a 15.3 percent BB% against a 21.2 percent K%. His 67 percent success rate on SB attempts wasn't great, but it was a small sample.
We don't have much data on Campbell, but what we have looks good. He also hit fifth on March 30 after beginning the year at the bottom of the lineup, suggesting the team will let him earn a more prominent role and the corresponding counting stats.
Fenway is a great place to hit, and he already made an appearance in the outfield that could lead to multi-position eligibility. Campbell looks like a Champ for 2025 and beyond.
