Mariners' Least-Discussed Trade May Have Decided Dodgers-Blue Jays World Series

The baseball world learned who Will Klein was on Monday...

Oct 27, 2025; Los Angeles, California, USA; Los Angeles Dodgers pitcher Will Klein reacts after the end of the eighteenth inning against the Toronto Blue Jays in game three of the 2025 MLB World Series at Dodger Stadium. Mandatory Credit: Kiyoshi Mio-Imagn Images | Kiyoshi Mio-Imagn Images

The Seattle Mariners would gladly have traded places with the Toronto Blue Jays, but Game 3 of the World Series on Monday night was still one of the more excruciating non-elimination losses in recent postseason memory.

In 18 innings, spanning six hours and 39 minutes, the Los Angeles Dodgers took down the Blue Jays 6 to 5 on a Freddie Freeman walk-off home run. Books could be written about that game, but here, we'll focus on just a single player of the 44 who appeared in the box score.

Dodgers pitcher Will Klein not only picked up the win in his second-ever postseason appearance, but he did so by throwing four innings of scoreless relief. Yet America might never have known his name, had the Mariners not made one of the most innocuous trades of the regular season.

Mariners' Will Klein trade suddenly got much more famous

Oct 27, 2025; Los Angeles, California, USA; Los Angeles Dodgers pitcher Will Klein (61) pitches against the Toronto Blue Jays in the eighteenth inning during game three of the 2025 MLB World Series at Dodger Stadium. Mandatory Credit: Jayne Kamin-Oncea-Imagn Images | Jayne Kamin-Oncea-Imagn Images

Klein, a 25-year-old former fifth-round pick, was in Triple-A with the Mariners for most of the first half of this season. He was traded to the Dodgers for lefty Joe Jacques, who appeared in zero games for Seattle at the major league level before electing free agency this winter.

But while Jacques was getting ready to pitch for the New York Mets, whom he already signed a minor-league contract with for next season, Klein was on the mound against the likes of Vladimir Guerrero Jr. and Daulton Varsho with the World Series potentially hanging in the balance.

In no way was Klein supposed to be in that situation. He only made 14 appearances for the team during the regular season, and he might not be on the World Series roster had setup man Alex Vesia not been forced to leave the team to deal with an emergency family matter.

But what mattered most was the fact that Klein was ready for his moment. It's hard to say he could have seen himself there when he was pitching to a 7.17 ERA in Triple-A Tacoma earlier this season, but a fresh start after his Mariners stint gave him all the opportunity he could have asked for.

It didn't end the series, but Klein's performance was worth 19.4% championship win probability added--just 5% less than Shohei Ohtani in the same game, and almost 30 points higher than Mookie Betts' contributions for the entire postseason. Now, just two more wins would get him a ring.

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