Red Sox make biggest Rule 5 addition via post-draft trade with Mets

The Boston Red Sox made a pair of additions during Wednesday's Rule 5 draft at the Winter Meetings in Nashville, Tennessee.

Although Boston opted not to use its own selection in the major league phase of the draft, they still left with an extra player on their roster, acquiring right-handed pitcher Justin Slaten from the New York Mets. The Mets had selected Slaten, a reliever, from the Texas Rangers with the eighth pick in the Rule 5 draft just moments earlier.

In exchange for Slaten, the Red Sox sent minor league reliever (and 2023 MLB Draft pick!) Ryan Ammons and cash considerations to the Mets.

Red Sox acquire Justin Slaten from Mets after 2024 Rule 5 Draft

Since Slaten was a Rule 5 selection, the Red Sox can protect him on their 26-man roster for the entire 2024 season. If they choose to outright him off the roster, he would be offered back to Texas for a $50,000 fee. Exceptions to this rule do exist, in case the player is removed from the 26-man roster due to injury.

Slaten is on a direct path to compete for a spot on the Opening Day roster. He made 40 appearances last season, amassing a 2.87 ERA, 1.07 WHIP, 12.97 K/9, and 3.02 BB/9. At first glance, his strikeout numbers jump off the page. He throws his fastball in the mid-to-upper 90s, but his best pitch is a slider that FanGraphs’ Eric Longenhagen described as “knee-buckling.”

New Red Sox Chief Baseball Officer Craig Breslow has shown a tendency to pursue young pitchers with above-average sliders in his first offseason with the club. On Tuesday evening, he acquired three pitchers with plus sliders in exchange for everyday outfielder Alex Verdugo.

Adding Slaten comes at a price, of course. Heading back to New York is Ammons, a 22-year-old southpaw whom Boston selected in the 10th round of last summer’s amateur draft. SoxProspects highlighted Ammons’ fastball and breaking ball as his best offerings, though we’ve yet to see them in a pro setting. Ammons has been sidelined with an injury ever since late July.

With the trade, Boston’s 40-man roster now stands at 38 players.

Red Sox add catcher Mickey Gasper in minor league phase

The Red Sox made just one addition during the minor league phase of the Rule 5 draft, selecting Mickey Gasper from the New York Yankees. He was announced as a catcher, but also spent time at first and second base during the 2023 minor league season.

Gasper is a native of Merrimack, New Hampshire. He attended college at Bryant University before finding his way to the Yankees as a 27th-round pick in the 2018 amateur draft. At 28 years of age, he’s on the older side for a minor league acquisition. Nevertheless, his defensive versatility fills an immediate need within the organization, given that the Red Sox previously had just one catcher on their Triple-A roster.

Between Double-A and Triple-A last year, Gasper slashed .246/.361/.375 with seven homers, 28 RBI, and 10 stolen bases. His 12.8 percent walk rate and 16.2 percent strikeout rate encapsulate his solid plate discipline.