The Orioles optioned left-handed pitcher Bruce Zimmermann to the alternate training site at Double-A Bowie on Monday night and recalled right-handed pitcher Isaac Mattson, who was on the taxi squad.

This is the second move the Orioles have made with a rookie starting pitcher. On April 18th, the  Orioles optioned Dean Kremer, Monday night’s starter against Seattle, in part to limit his innings.

Zimmermann, who is 1-3 with a 5.40 ERA in six starts, allowed four runs, one unearned, on seven hits in 4 2/3 innings at Oakland on Sunday.

The Orioles have offdays on Thursday, May 13th and May 17th.  They’ll need a fifth starter on May 11th, and  again on May 22nd. Zimmermann is eligible to be recalled in 10 days, so barring injury, someone besides him will have to make that May 11th start against the New York Mets at Citi Field.

Mattson, who was at the alternate training site and has not pitched in the major leagues, was obtained in the December 2019 trade with Los Angeles for Dylan Bundy. The move gives the Orioles 10 relievers.

Stewart scratched: DJ Stewart, who was in Monday’s lineup as the rightfielder, was scratched because of lower back stiffness. Manager Brandon Hyde said that the injury was day-to-day and not related to Stewart’s bullpen collision in Oakland on Saturday. Stewart hit the bullpen awning while running at full speed to catch a popup.

Hyde made multiple changes to the lineup for the first game against the Mariners. Ryan Mountcastle is starting in left, Austin Hays in right, Maikel Franco at designated hitter, Rio Ruiz at third and Pat Valiaka at second.

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