SAN FRANCISCO — The San Francisco Giants made a notable addition to their infield Monday, acquiring former top prospect Marcelo Mayer from the Boston Red Sox in exchange for left‑handed reliever Erik Miller and outfield prospect Carlos Gutierrez. The move delivers San Francisco a high-upside infielder once regarded as one of baseball’s premier young talents, while Boston adds a dominant bullpen arm and a fast‑rising outfielder.
Mayer Brings Premium Pedigree and Upside to San Francisco
Mayer, 23, appeared in 70 games for Boston this season before landing on the injured list June 26 with a bone stress reaction in his left ulna. He hit .220 with 10 doubles, three home runs, 22 RBI, and a .594 OPS, splitting time between second base and shortstop.
The Chula Vista, Calif., native has long been considered one of baseball’s elite prospects. MLB.com ranked him among the Top 15 overall prospects for four consecutive seasons: No. 12 (2025), No. 15 (2024), No. 9 (2023), and No. 14 (2022). Selected fourth overall in the 2021 MLB Draft, Mayer earned Futures Game selections in both 2023 and 2024.
Across 114 career major league games, all with Boston, Mayer owns a .223 average, seven home runs, 32 RBI, and a .624 OPS.
Miller Heads to Boston After Breakout Season in Giants Bullpen
Miller, 28, has been one of San Francisco’s most effective relievers this season, posting a 2–0 record, 2.76 ERA, four saves, and 45 strikeouts across 38 appearances. His underlying metrics place him among the most dominant left-handed relievers in the sport.
Statcast ranks Miller in the:
- 99th percentile in average exit velocity
- 98th percentile in expected batting average
- 98th percentile in hard-hit rate
- 97th percentile in whiff rate
- 95th percentile in strikeout rate
- 92nd percentile in ground-ball rate
He has delivered 14 consecutive scoreless outings dating back to June 19.
Across three MLB seasons (2024–26), all with the Giants, Miller owns a 3.05 ERA with 154 strikeouts in 147 appearances.
Gutierrez Adds Speed and Offensive Production to Red Sox System
Gutierrez, 21, has been one of High‑A Eugene’s most dynamic players this season, hitting .271 with an .826 OPS, 18 doubles, nine home runs, 45 RBI, and 26 stolen bases across 83 games. Ranked No. 24 in the Giants’ system by Baseball America, the left-handed hitter has shown consistent growth since signing as an international free agent in 2023.
Across 168 career minor league games, Gutierrez owns a .314 average, .866 OPS, 64 steals, and 85 RBI.
The trade marks a significant organizational shift for both clubs: San Francisco secures a former top draft pick with long-term upside, while Boston adds a high-impact bullpen arm and a versatile outfield prospect as it continues to reshape its roster.
