Mariners add Josh Naylor, option Miles Mastrobuoni

Mark J. Rebilas-Imagn Images

The Mariners made their lineup deeper and their bench shallower on Friday.

They added Josh Naylor to the active roster and optioned Miles Matrsobuoni to Tacoma. The moves come a day after the Mariners acquired Naylor in a trade with the Diamondbacks.

The Mariners could have moved on from the severe struggles of Donovan Solano or Dylan Moore but instead optioned Mastrobuoni, raising a number of questions about how the lineup will operate going forward.

Naylor is a lefty first baseman with large handedness

splits (144 wRC+ vs. RHP; 88 wRC+ vs. LHP). The Mariners have used a platoon at first base all year, with Rowdy Tellez and Luke Raley against RHP and Solano against LHP. On the one hand, it’s worked, as the Mariners have a 126 wRC+ at first base against RHP. On the other, it hasn't worked, as they have a 40 wRC+ at first against LHP — worst in MLB. That split also doesn’t include Solano’s 1-for-23 as a pinch hitter.

Naylor could represent an improvement for the Mariners at first base against LHP, but it’s not clear if they plan to use him as a starter or as another platoon bat. Solano’s last remaining role with the team appears to be as the short side of a first platoon, whereas Mastrobuoni could play just about every position on the field. Mastrobuoni has struggled this year with an 86 wRC+, but so has Solano with an 82 wRC+. Kate Preusser also recently noted for the site that Matsrobuoni has been quite good off the bench, and the Mariners seemed pleased with what they got from him this year. Perhaps Solano remaining on the team implies he’s still in the platoon.

We could get that answer tonight. Naylor will bat fourth in the lineup.

The Mariners face RHP in José Soriano to begin the game, but the Angels have three LHP in the bullpen. If Naylor gets to face one late, and especially if he starts against LHP Tyler Anderson on Saturday, that bodes well for his future as the team’s true first baseman.

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