The San Francisco Giants might spend part of this winter looking for a pitcher like the one they traded in August. Erik Miller missed bats from the left side, handled late innings, and was still years away from free agency. That's a useful combination for a team that needs to rebuild its bullpen.

The Giants acquired infielder Marcelo Mayer from the Boston Red Sox on Aug. 3 in exchange for Miller and minor league outfielder Carlos Gutierrez. The calculation was different from the one San Francisco faced when it dealt Robbie Ray and Tyler Mahle. Both starters were headed for free agency, so trading them turned a few remaining weeks into younger pitching.

That made Miller the tougher player to give up. By trading him for Mayer, the Giants bet that a potential everyday infielder was worth more than the relief innings Miller could give them in 2027.

What the Giants Lost in Miller

Miller posted a 2.76 ERA with 45 strikeouts in 32.2 innings for San Francisco. He kept missing bats in Boston, striking out 29 in 18.2 innings with a 3.38 ERA. The concern was his control: Miller walked 34 batters in 51.1 innings overall. The Giants could have used his strikeouts in the seventh and eighth innings without counting on him to close.

MLB Trade Rumors projected a $1.5 million salary for Miller in 2027, his first year of arbitration eligibility. He was also on track to remain under club control through 2029. Those terms would have given San Francisco room to pay for another late-inning arm while keeping one it already knew.

The Giants finished 2026 with a 4.14 bullpen ERA and 27 blown saves, which put relief help high on their offseason priority list. Keeping Miller would have covered one role in a bullpen that still needed work. Filling that role now takes money, a trade, or a bet on a less proven pitcher.

How Mayer Can Make the Trade Pay Off

Mayer gave San Francisco a chance to fill a more valuable position. The No. 4 pick in the 2021 MLB draft hit .271/.347/.471 with nine home runs in 43 Triple-A games in 2025. He also started 39 games at second base for Boston in 2026, giving the Giants an obvious place to try him.

A bone stress reaction in his left forearm kept Mayer out until Sept. 21. He hit .067/.176/.067 in six games for San Francisco, a 17-plate-appearance sample that said little about what he could do with steady at-bats. As On SI's earlier look at the Mayer trade explained, the Giants still needed time to evaluate him.

Mayer should get a chance to compete with Casey Schmitt for time at second base. If Mayer stays healthy, gets on base and earns regular starts, that's a return worth giving up a reliever for. If he settles into a bench role, San Francisco will still need a starting second baseman and will have surrendered an affordable source of strikeouts.

Mayer has time to make the deal work. The Giants have this winter to replace the innings they gave up.