MLB Prospect Debuts: Fantasy Baseball Waiver Wire Pickups and Rookie Stashes (Week 8)

Fantasy Baseball Hitter Prospects To Target

Colt Emerson, SS, Seattle Mariners (22% rostered)

Level: MLB

2026 Stats: 169 PA, .255/.347/.469, 26 R, 7 HR, 26 RBI, 10 SB, 10.1% BB%, 27.2% K%, 105 wRC+

The Mariners have called up their No. 1 prospect, Colt Emerson, after veteran infielder Brendan Donovan landed on the injured list with a groin injury. Donovan is expected to miss more than the minimum 15 days, and even if he returns quickly, Emerson could stick around if he proves he’s ready for the majors.

The bigger question is what happens when Donovan returns, as Seattle’s current shortstop, J.P. Crawford, could end up blocking Emerson’s path to regular playing time.

Crawford has been productive this season, posting a 120 wRC+ across 41 games, but at this stage of his career, he profiles more as a below-average overall infielder with a solid bat. Emerson, meanwhile, is viewed as the future of the organization. Earlier this year, Emerson signed an eight-year, $95 million extension, a clear signal that the Mariners are fully committed to his long-term role with the club.

Unfortunately, unlike Konnor Griffin and Kevin McGonigle, Emerson currently projects to be a better real-life baseball player than a fantasy asset in 2026. Even so, it’s rarely a bad idea to pick up a top-10 overall prospect. So far at Triple-A this season, the left-handed-hitting Emerson has recorded seven home runs and 10 steals while posting a 27.2% strikeout rate and a 10.0% walk rate across 169 plate appearances, good for a 105 wRC+.

Here is a Statcast breakdown of his Triple-A performance.

While those numbers may not immediately jump off the page, it’s important to note that he suffered a minor wrist injury earlier in the year, which delayed his initial MLB call-up. Now that he is fully healthy, what should fantasy managers expect? If he stays up the rest of the season, Emerson could hit up to 10 home runs while swiping 10 bags with a .235 average.

Overall, he profiles as a rosterable middle-infield option in a 15-team league, but buyer beware, it is not a forgone conclusion that he will stay up or be an above-average bat to start his career.

Fantasy Baseball Pitcher Prospects To Target

Connor Prielipp, SP, Minnesota Twins (16% rostered)

Level: MLB

2026 Stats: 25.0 IP, 2.88 ERA, 0.96 WHIP, 28.4% K%, 8.8% BB%, 4.18 FIP

Connor Prielipp would likely be a much bigger name in fantasy baseball if injuries hadn’t slowed his development. The 25-year-old underwent Tommy John surgery in 2021 at the University of Alabama and has also dealt with minor shoulder issues since then, which has led the Twins to limit his innings. Now he finally looks healthy again, and the results have been excellent at the big-league level.

One of the biggest reasons for his instant success is his MLB-ready arsenal. Prielipp boasts a five-pitch mix led by a mid-90s fastball and a 70-grade slider that has already produced a 29% whiff rate. His changeup grades out as slightly above average and helps neutralize right-handed hitters, while his curveball effectively changes eye levels and disrupts hitters’ timing.

Connor Prielipp's 2Ks in the 1st pic.twitter.com/qkHfXG4kxU

— Rob Friedman (@PitchingNinja) May 16, 2026

Prielipp's success is also supported by his underlying metrics: 105 Stuff+, 104 Location+, and 103 Pitching+. So, what should we expect moving forward? OOPSY projections, which incorporate Stuff+ and Statcast data, forecast him for a 3.80 ERA, 1.28 WHIP, with a 24.8% strikeout rate and a 9.2% walk rate. For the foreseeable future, Prielipp should be rostered in all leagues, but you should be aware that eventually, he will be shut down.

As we discussed, the Twins have been very careful with his workload. He threw a career-high 82 2/3 innings last season and is already up to 40 2/3 innings this year. Because of that, Prielipp is a strong sell-high candidate if you can move him, but if you can't, make sure you have a backup plan for the final stretch of the season.

River Ryan, SP, Los Angeles Dodgers (11% rostered)

Level: Triple-A

2026 Stats: 11.0 IP, 4.09 ERA, 1.27 WHIP, 29.2% K%, 6.3% BB%, 2.45 FIP

Over the weekend, Dodgers manager Dave Roberts said there is a “slim possibility” that River Ryan could join the starting rotation in place of the injured Blake Snell (elbow). The Dodgers first called Ryan up in 2024, when he threw just 20 1/3 innings, posting a 4.50 SIERA, 1.33 WHIP, and an 11.1% K-BB% before suffering an elbow injury. That setback ultimately required Tommy John surgery, causing him to miss the entire 2025 season.

Before the injury, Ryan was widely viewed as one of the top pitching prospects in baseball because of his electric stuff and deep arsenal. The 27-year-old features a six-pitch mix highlighted by a mid-90s fastball and a devastating slider that has already found success in the Show. He also mixes in a cutter, sinker, curveball, and changeup. Here is a look at his most recent start against the Albuquerque Isotopes.

River Ryan is looking NASTY down in OKC 😮‍💨#Dodgers #BlueDynasty pic.twitter.com/fRd1MDoHrX

— Blue Dynasty (@D_BlueDynasty) May 16, 2026

At some point this season, Ryan is expected to earn a call-up to the major league roster. Once he puts on Dodger blue, he will be a must-roster player in all fantasy formats due to his strong prospect pedigree, returning velocity, and the win potential that comes with pitching for such a talented team. He is already worth stashing in deeper 12-team leagues if you have the roster space available.