Mariners now on the defensive after Rangers' MacKenzie Gore trade jolts AL West

Since opening their offseason with a bang by securing Josh Naylor in November, the Seattle Mariners have been content to merely improve on the margins. That has grown increasingly frustrating, and now looks like a problem after what the Texas Rangers did on Thursday.

They now have MacKenzie Gore as part of their starting rotation, with Jon Heyman of the New York Post reporting first that the All-Star left-hander was headed to Texas. The Washington Nationals are getting five players out of the deal, which tells you how much the Rangers think Gore can help them catch the Mariners in the AL West.

Rangers' MacKenzie Gore stunner puts the Mariners on the defensive

The last thing the Rangers needed was more starting pitching. Their starters led the majors with a 3.41 ERA in 2025, and the main contributors — Jacob deGrom, Nathan Eovaldi and Jack Leiter — were always set to return for 2026.

That Texas wanted Gore anyway feels like classic Chris Young. Go figure that a former pitcher-turned-GM would love himself some pitching, and Gore now stands to be one of the best No. 3 starters in all of MLB for his club.

The 26-year-old has had ups and downs as a pro, but he's on an upswing after the last two seasons. He's made 30-plus starts in each, and was good enough to make his first All-Star team in 2025. Though his ERA finished at 4.17, nobody wants to mess with a lefty whose whiff and strikeout rates were both in the 80th percentile.

According to FanGraphs' projections for 2026, the Mariners still project for the most WAR (45.0) of any team in the AL West. Yet the Houston Astros (42.2) aren't far behind, and the Rangers (39.5) will have their gap cut down once the model accounts for Gore.

"Bring it on" could be the Mariners' default position, as they indeed had winning records against both Texas clubs in 2025. But both of them had down years, and each now has momentum in their efforts to turn the tide. Before the Rangers added Gore, the Astros had delivered their own broadside against Seattle by winning the Tatsuya Imai sweepstakes.

As other teams position themselves to make noise on the trade market, the Mariners have the excuses they need to finish their offseason with a proper flourish. A trade for Brendan Donovan has been their ideal solution for months at this point, and now it looks like more of a necessity than a luxury.

Though the Mariners' real goal for 2026 is to win the World Series, capturing a second straight AL West title needs to come before that. And right now, they'd do well to not take that for granted.