The Seattle Mariners picked up an extra base runner that turned about to be very important thanks to a rare challenge in Thursday’s win in Kansas City.

Mariners return to first place in AL West, close in on first-round bye

After Mariners right fielder Dominic Canzone grounded out to Royals second baseman Michael Massey for the second out in the top of the eighth inning, Seattle manager Dan Wilson emerged from the dugout and asked to have Massey’s defensive positioning reviewed.

Per MLB’s defensive shift rules, infielders cannot be on the outfield grass when the pitcher is on the rubber. And as it turned out, the very back of Massey’s cleats were indeed on the grass before the pitch to Canzone.

After the play was reviewed at MLB’s replay command center in New York, Canzone was awarded first base, with Massey charged with an error.

The challenge came on a tip from Seattle replay coordinator Andy Bissell, and it proved to be huge for the Mariners.

“There was just enough evidence to show his heel was in the grass.”

Andy Bissell (Major League Replay Coordinator) discussed what led to the #Mariners replay challenge in Kansas City. (🎥 @shannondrayer) https://t.co/jHnqN7RvB3 pic.twitter.com/YV2bdFoXvQ

— Seattle Sports (@SeattleSports) September 18, 2025

First, it prompted Kansas City to go the bullpen, ending a strong day for starting pitcher Stephen Kolek.

Second, it led to a very important insurance run for the Mariners.

Seattle replaced Canzone with pinch-runner Victor Robles, and two batters later, Robles took off on the same pitch that J.P. Crawford ripped down the right-field line. Robles scored to make it a 2-0 Mariners lead, which was the eventual final score.

Adding on! #TridentsUp pic.twitter.com/uCRVR984mF

— Seattle Mariners (@Mariners) September 18, 2025

The M’s picked up a series win Thursday over the Royals at a very crucial time in their season. The victory pulled them into a tie at 84-69 with the Astros for first place in the AL West before beginning a three-game series in Houston on Friday. The M’s also maintained a lead of 2 1/2 games for the American League’s final wild card spot, and moved within one game of the AL Central-leading Detroit Tigers for the second seed in the AL.

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