A's Finally Addressing an Area of Need With Latest Roster Move

This move will make it harder on Seattle's bats throughout the series

Mar 7, 2026; Mesa, Arizona, USA; Athletics pitcher Mason Barnett (63) throws against the Chicago Cubs in the first inning at Sloan Park. Mandatory Credit: Rick Scuteri-Imagn Images | Rick Scuteri-Imagn Images

On Sunday, A's manager Mark Kotsay was talking about the team's bullpen usage heading into this week's series with the Seattle Mariners—one which could have season-long implications against the favorites to win the division.

Kotsay brought up the team's lack of a second left-handed pitcher in the bullpen aside from Hogan Harris, and that the Seattle Mariners are a lefty-heavy group on offense. That could lead to some challenges this week, with Harris unlikely to pitch a significant role in each of those three games.

That's why the A's made another roster move on Monday afternoon, calling up left-hander Brady Basso. In a corresponding move, the club optioned Mason Barnett down to Triple-A Las Vegas. Kotsay, said that we nailed the analysis and that he was up to cover innings ahead of the Seattle series. Now the A's are after a different tool in their toolbox.

This season Basso has made six appearances spanning 6 2/3 innings and holds a 9.45 ERA (5.14 FIP) with a 55% ground ball rate and a 25% strikeout rate. He's also more in the zone than most A's pitchers this season, holding a 9.4% walk rate in the minors.

The two big reasons for his high ERA to date are his 55.6% left on base rate, meaning that when runners get on, they're often coming around to score, and his .474 BABIP, which is an indicator of some bad luck. The hope is that with some big-league gloves behind him, that luck turns around and he can be effective in this series.

Seattle against left-handers

Apr 15, 2026; San Diego, California, USA; Seattle Mariners right fielder Luke Raley hits a two-run home run during the fifth inning against the San Diego Padres at Petco Park. All MLB players are wearing number 42 today to honor Jackie Robinson. Mandatory Credit: Denis Poroy-Imagn Images | Denis Poroy-Imagn Images

As we mentioned this morning, Seattle doesn't produce a ton of hits, but they do walk a ton. Their 11.5% walk rate as a team ranks fifth in baseball. While they have hit .216 as a team, they're still getting on base at a .320 clip.

Three of Seattle's everyday bats are lefties, while they have two more that are platoon options (Luke Raley and Dominic Canzone). In addition, they also boast two switch hitters in Cal Raleigh and Leo Rivas, so the key for Kotsay and the A's will be getting the right matchups later in the game.

With that versatility from Seattle, having a second left-hander will ensure that more matchups can tilt in the A's favor.

The Mariners have also struggled mightily against left-handed pitching this season, posting a 66 wRC+ (100 is league average) as a team, which ranks them 27th in baseball. The A's have also struggled, posting a 65 wRC+ and sitting right behind Seattle.

Randy Arozarena, (203 wRC+), Cole Young (166) and J.P. Crawford (157) are the three bats that have produced above league average numbers against southpaws, so it will be interesting to see how Seattle's lineup is constructed to attempt to halt the A's plans of attack against the rest of the roster.

This series is going to be filled with plenty of back-and-forth moves, but will ultimately come down to which team gets the timely hitting, and whether the A's can limit the free passes in the next three days.

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