Ahead of Saturday night’s game in Seattle, the Boston Red Sox placed veteran utility man Isiah Kiner-Falefa on the 10-day injured list with left forearm inflammation. The injury to the 31-year-old puts the Red Sox' middle infield depth to the test. 

The Red Sox were already without infielder Nick Sogard, who has been on the injured list since June 3 (retroactive to May 31) with a right oblique strain, and Romy Gonzalez, who has missed the entire 2026 season after undergoing offseason shoulder surgery. Gonzalez, who is on a rehab assignment with Double-A Portland, had his timeline delayed due to hip flexor soreness. Shortstop Trevor Story underwent sports hernia surgery on May 22 which will keep him out until late July. 

The string of injuries had forced Kiner-Falefa from a seldomly used bench player to a regular at second base. The setback for Gonzalez could not have come at a worse time for Boston, as now, in Kiner-Falefa’s absence, it will be a combination of Andruw Monasterio and the freshly recalled Anthony Seigler to fill in at second base. 

The 29-year-old Monasterio figures to draw into the lineup against lefties, where he has a .252/.345/.396/.740 and a wRC+ of 108 in 264 plate appearances in his career. 

He has, however, struggled in his first season in Boston, hitting .237/.281/.377/.658 with a 77 wRC+. In 453.1 innings at second base, Monasterio has posted a defensive runs saved of four, an outs above average of -4, and a fielding run value of -2. 

The 27-year-old Seigler was acquired alongside Monasterio and third baseman Caleb Durbin in an offseason deal with the Milwaukee Brewers. 

He appeared in two games during his first stint in Boston, going 1-for-3 with a double. In 37 games for Worcester, Seigler has hit .290/.409/.435/.844 with three home runs and 23 RBI. He has played nearly 1500 innings at second base since 2023. 

Seigler will lead off and play second in Boston’s Saturday night matchup in Seattle with the Mariners. 

While Monasterio and Seigler will likely get the first crack at replacing Kiner-Falefa, Boston does have a pair of potential replacements in Worcester in Vinny Capra and Tsung-Che Cheng. 

Capra has spent parts of four seasons in the big leagues with Toronto, Pittsburgh, Milwaukee, and Chicago, where he has struggled at the plate. In 142 major league plate appearances, the 29-year-old has hit just .133/.181/.188, while spending the majority of his time defensively at third base. 

In 54 games with Triple-A Worcester, Capra has hit .270/.366/.413/.779 with four home runs and 31 RBI. Throughout his professional career, Capra has limited experience at second base, playing only 44.1 innings in the majors. In addition to his lack of experience at the position, Capra is not on the Red Sox 40-man roster, so he would require a roster move to be called up to Boston.  

The Red Sox could also turn to shortstop Tsung-Che Cheng if Monasterio and Seigler are unable to produce. 

The 24-year-old made his major league debut with Pittsburgh in April 2025, going 0-for-7 in three games. After bouncing around the waiver wire throughout the offseason, Cheng was claimed off waivers by the Red Sox in early February. 

In 60 games for Worcester, Cheng has hit .259/.357/.434/.791. Unlike Capra, he has more experience handling second-base duties, playing over 1,000 innings at the position since 2021, including over 600 in Worcester. Cheng is also already on the 40-man roster, making him much more likely to be the move if the Red Sox do choose to go that route. 

Given that neither Monasterio nor Seigler is a fantastic option to spell Kiner-Falefa, paired with Capra’s inexperience at the position and the relative unknown of Cheng. Red Sox interim manager Chad Tracy could choose to play Durbin at second base and outfielder Nate Eaton at third. 

Throughout spring training, there was a discussion about which one of Durbin and Mayer would play second and third base, before the team eventually settled on Mayer at second and Durbin at third. 

Eaton has only appeared in three games since being recalled on June 8, going 0-for-3 at the plate. 

It would be hard to imagine Tracy would choose to move Durbin off of third base, given he is tied for the second-most outs above average at the position with seven. And especially considering Eaton has struggled defensively at third base, posting a -7 outs above average in 187.1 big league innings at the position. 

The middle infield group was one of the deepest original groups on the roster, but now depth will really be tested in the coming weeks with Kiner-Falefa down and Gonzalez’s rehab slowed. 

The Red Sox will look to take the series from the Mariners on Saturday night in game two of a three-game set. Connelly Early (5-5, 3.81 ERA) will get the start for Boston opposite Emerson Hancock (5-3, 3.28 ERA) for Seattle. First pitch from T-Mobile Park set for 10:10 p.m. ET. 

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