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Three top fantasy baseball prospects - Colson Montgomery, Anthony Seigler, Shinnosuke Ogasawara - that can make big impacts. These MLB prospects are waiver wire pickups or stashes.
During the first half of the campaign, fantasy managers have seen several high-end prospects get the call to the big leagues. Boston's top prospect, Roman Anthony, earned the call in June and is beginning to turn the corner following his slow start.
In this piece, we will look at three players who recently made their MLB debut and determine if they are holding on our fantasy roster.
Should those players be left on the waiver wire, or should fantasy managers add them before their breakout? Let's dive in!
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Colson Montgomery, SS, Chicago White Sox
Current Level: MLB
Availability: 15% rostered
2025 MLB stats: 4 G, .385/.500/.538, 1 3B, 3BB, 3 SO
Colson Montgomery got the call to join the White Sox and has been quite hot. After going hitless in his debut, Montgomery had a three-hit night in his second game, which included a triple and a two-hit performance on Sunday. I believe Montgomery is a great buy for fantasy players in both Redraft and Dynasty at this point, given some struggles that may not be as reflective under the hood.
Montgomery was bad in Triple-A to start the season. Before hitting the development list, Montgomery was striking out in 42 percent of plate appearances and had a slash line of .149/.223/.255 in 103 trips to the plate. While at the White Sox complex in Camelback Ranch, he had a mental and mechanical reset. He did not return perfectly, but there were major improvements despite playing through an injury in May.
Under the hood, the power has looked good all year. Montgomery has a 115.3 mph max exit velocity and a 90th percentile exit velocity of 108 mph. Surprisingly, the season-long zone contact is north of 85 percent, and the chase rate is just shy of 30 percent for the season.
The strikeouts are still an issue, but Montgomery is showing positive signs, which is good for the former top White Sox prospect. He is in for a big bounceback. I am in.
Through his first four games in the big leagues, Montgomery has posted two multi-hit outings. In addition, through this short stint, Montgomery has been able to keep his strikeouts low and has been able to draw walks at a 17.6% rate. He has started each game at shortstop and should be expected to see the majority of opportunities there during the second half.
He is worth adding in all 12+ team redraft leagues.
CATCH OF THE SUMMER⁉️ #SCTop10
COLSON MONTGOMERY, HOW DO YOU DO‼️
(via @MLB)pic.twitter.com/jICxY3tD4y
— SportsCenter (@SportsCenter) July 5, 2025
-Written by Chris Clegg
Anthony Seigler, INF/C, Milwaukee Brewers
Current Level: MLB
Availability: 5% rostered
2025 MLB stats: 4 G, .125/.125/.125, 1 H, 1 SO
Anthony Seigler's long journey in professional baseball has now seen him join the Brewers roster. Seigler has been in the minors since 2018 but has some pedigree as a former first-round pick. Selected by the Yankees out of Cartersville High School, Seigler received a $2.8 million bonus. He joined the Brewers organization this offseason and looks like a different player.
Seigler is hitting, and that has continued all season. He got on base in 55 of his 62 minor league games before earning the call to the Majors. From May forward, Seigler slashed an impressive .315/.438/.510 with as many walks as strikeouts. For the season, Seigler is slashing .277/.416/.465 with seven home runs and 20 stolen bases.
As you might expect from the high OBP, Seigler rarely chases pitches out of the zone, having an O-swing rate of 19 percent. The contact is good, as Seigler connects on 78 percent of swings overall and 85 percent in the zone.
While he may not be a huge source of power, Seigler consistently hits the ball hard, with a 45 percent hard-hit rate and a 91.6 mph average exit velocity. His versatility is highly attractive for the Brewers, as Seigler can catch or play in the infield. While he may not play every day in a Brewers uniform, he stands a good chance of hitting his way into a bigger role.
The versatility only helps.
Through his first week in the majors, Seigler has only seen two starts (out of seven games), which will limit his value in shallower redraft leagues. Given his unattainable playing time at the moment, he should only be rostered in deeper NL-only leagues for redraft and dynasty formats.
In 2017, Anthony Seigler was a switch hitter, switch-throwing catcher AND a switch pitcher! 😳
Now after a winding career, the Brewers are calling him up to the majors. https://t.co/VNocztjtP5 pic.twitter.com/1eBj6bRm4g
— Baseball America (@BaseballAmerica) July 1, 2025
- Written by Chris Clegg
Shinnosuke Ogasawara, SP, Washington Nationals
Current Level: AAA
Availability: 10% rostered
2025 MiLB stats: 24 IP, 4.50 ERA, 1.21 WHIP, 24 SO, 6 BB
Ogasawara is an interesting "prospect" signed from Japan in January 2025. Signed to a two-year contract by Washington, he did not make the team out of spring training. At 27, he got the call last week and debuted with just over two innings, allowing four runs and seven hits while striking out only two Boston Red Sox hitters.
Given the paucity of Washington starters right now, he slots into the rotation and is slated to get the Milwaukee Brewers this weekend.
Shinnosuke Ogasawara’s MLB debut finishes in the 3rd inning after 55 pitches.
2.2 IP, 7 H, 4 R, 0 BB, 2 K, 1 HR
Cole Henry came in to finish the inning and strand the runners left at first and third. pic.twitter.com/TQ26aE3Np4
— Tobi Altizer (@Tobi_Altizer) July 6, 2025
Earlier this season, Ogasawara logged just 24 innings in the minor leagues before earning the call to the big leagues. At Triple-A, he made just three starts (15 innings pitched) and posted a 4.80 ERA with a 1.33 WHIP. He showed strong command, allowing just four walks while striking out 12 hitters.
The lefty looks to be fairly typical of Japanese hurlers; he doesn't have much velocity but relies on great command, control, and guile. See below. I recognize it is a two-inning sample, but Ogasawara threw four of his pitches over 20% of the time and never topped out at more than 90 miles per hour.
He is going to get by on inducing groundball outs, and his career-best strikeout percentage was 24% in 2022.
Given his lower strikeout upside, he is best left on the waiver wire in shallow redraft leagues. However, Ogasawara could find value in deeper formats, especially when looking to boost your WHIP ratio given his strong command.
- Written by Mike Carter
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