Giants Designate Mason Black, Acquire Justin Dean and Reiver Sanmartin
The San Francisco Giants have made significant moves as they kick off the offseason. In a sudden flurry of activity, they designated right-handed pitcher Mason Black for assignment. At the same time, they claimed outfielder Justin Dean and left-handed pitcher Reiver Sanmartin off waivers.
Details of the Transactions
The Giants announced these changes through social media after issuing a press release. They had an opening on their 40-man roster following the decision to decline Tom Murphy’s contract option.
Justin Dean: New Outfielder
Justin Dean, a right-handed hitter approaching his 29th birthday, comes from the Dodgers after being designated for assignment. Originally drafted by the Atlanta Braves in the 17th round in 2018, Dean spent most of the 2025 season in the AAA league. There, he achieved a batting line of .289/.378/.431, along with six home runs in 347 plate appearances.
- Proficient defensive player with a history of strong on-base skills.
- Notable for his speed, stealing 89 bases over two years.
- Had limited exposure in the Major Leagues, playing 18 regular-season games with only two plate appearances.
- Participated in 13 postseason games without a plate appearance.
- Holds three Minor League options remaining.
Reiver Sanmartin: Left-Handed Pitcher
Reiver Sanmartin, also 29, joins the Giants after a stint with the Cincinnati Reds. He made his Major League debut in 2021 and has played in all subsequent seasons, with 2022 marking his most established role.
- Has a career ERA of 5.66 and a FIP of 4.45 over 62 appearances.
- Recorded 73 strikeouts against 42 walks in 84.1 innings pitched.
- Struggled in the Majors this year, but had a strong showing in AAA with a 2.67 ERA over 67.1 innings.
- Utilizes a four-pitch mix: four-seam fastball, sinker, slider, and changeup.
- Possesses one Minor League option remaining.
Mason Black: Designated for Assignment
Mason Black, a third-round draft pick in 2021, faced a challenging 2025 season. He achieved a 5.81 ERA and 5.64 FIP in AAA, managing only one Major League appearance. With one Minor League option available, there is a possibility that he may be claimed by another team. If not, the Giants can retain him in their system by assigning him to AAA Sacramento.
These roster changes highlight the Giants’ strategy to adjust their team composition as they prepare for the upcoming season.
