The Red Sox Offseason Starts With Roster Math: Cheng to Detroit, Eaton to the A's, and Sonny Gray Hits Free Agency

The Red Sox offseason did not open with a blockbuster. It opened with a spreadsheet. On Oct. 29, Boston traded infielder Tsung-Che Cheng to the Detroit Tigers for cash considerations and traded outfielder Nate Eaton to the Athletics for right-handed pitcher Jareth Rayo, according to the team's official transaction log. A day later, right-hander Sonny Gray elected free agency.

The reason is the 40-man roster. Teams have to make room for players coming off the 60-day injured list once the season ends, and the Red Sox needed to open spots, MLB.com's Jason Beck reported. Detroit made its move for Cheng before he could be exposed to waivers, where he had been claimed several times last offseason.

Cheng's path to Boston was one of those only-in-baseball stories. The 25-year-old, a 5-foot-8, left-handed-hitting shortstop and second baseman from Taiwan, signed with the Pirates in 2019 and spent five years in their system, MLB.com reported. Then he was claimed off waivers by the Rays, then the Mets, then the Nationals, and finally the Red Sox, all within about a month.

He made his MLB debut with Pittsburgh in 2025 and went 0-for-7 in three games. He got his first big-league hit in his Red Sox debut on June 26 this season. In 14 games with Boston, he went 10-for-39, a .256 average, with five RBIs, before going back to Triple-A Worcester, where he hit .241 with a .345 on-base percentage, eight home runs and 30 RBIs in 94 games, according to MLB.com.

He also played for Chinese Taipei in the World Baseball Classic, going 3-for-9 with five walks and four stolen bases in four games, alongside Tigers infielder Hao-Yu Lee. MLB.com said he will likely be organizational depth in Detroit, where the Tigers have their own 40-man crunch: 36 players on the roster, not counting eight on the 60-day IL, and spots to open by Monday.

The Eaton trade is the more interesting one for Boston's future. The Red Sox got Rayo, a right-handed pitcher, in exchange for an outfielder who was on the 40-man roster, according to the transaction log. That is a classic offseason move: turn a roster spot you need back into a prospect who does not need one yet. The team's log does not list Rayo's level or age, and Boston had not released a statement on him as of Friday.

Then there are the free agents. Gray elected free agency on Oct. 30, the log shows. Left-hander Patrick Sandoval and infielder Isiah Kiner-Falefa elected free agency on Oct. 29. Those are not trades or releases; the players chose to test the market, and the team's log lists them as elections, not moves the club made.

Gray's decision matters most. A veteran starter leaving opens a hole in the rotation that the front office will have to fill through free agency or a trade, and the log does not say whether the Red Sox made any effort to re-sign him before he elected free agency.

What this week tells you is how tight the roster is. When a team trades a 25-year-old infielder for cash and a 40-man outfielder for a pitching prospect within the same day, it is not because it does not like either player. It is because it needs the space, and more spots will have to open as players come off the injured list.

The other thing to watch is waivers. Cheng's history shows how quickly teams grab cheap infield depth in the fall. By trading him instead of trying to sneak him through waivers, Boston at least got something back, even if it was only cash.

And in fairness to the front office, this is when every team does this. Detroit has its own version of the same problem and has to clear spots for eight injured players by Monday. Boston is not doing anything unusual. It is just doing it in public, one line of the transaction log at a time.

None of this is the kind of move that makes a fan base excited for spring. But it is the kind of housekeeping that determines how much room the front office has when the bigger decisions come, and it is happening on schedule.

What we still don't know: how many more 40-man spots the Red Sox need to open, whether Gray could return on a new deal, and where Rayo will start his Red Sox career.