Bryan Woo has been on a rollercoaster ride this season, and while Mariners fans might be tempted to breathe easy after his latest start, I'm not ready to let go of the fence just yet.

Let's rewind to April 25th, when Woo delivered what can only be described as the worst outing of his professional career. If that wasn't alarming enough, he followed it up with another bottom-10 performance against the Royals. Over those two games combined, he managed just three strikeouts while surrendering 16 hits and—brace yourself—six home runs. Yes, six. It's the kind of stretch that makes even the most optimistic fan wince.

So when Woo took the mound against Atlanta on Wednesday and delivered a gem—6 innings, 0 runs, 1 hit, 2 walks, and 9 strikeouts—you could almost hear the collective sigh of relief from the Pacific Northwest. But I'm not exhaling yet.

Here's why: Woo's pitch mix is raising red flags. Even for a pitcher who leans heavily on his four-seam fastball, Wednesday's usage rate of 66% is extreme. He typically balances those heaters with a healthy dose of two-seamers, but he threw just seven sinkers against Atlanta—the second-fewest of his entire career. That's not a coincidence; it's a pattern.

And the numbers back up the concern. After posting solidly positive run values on his sinker over his first three seasons, that pitch has taken a nosedive in 2025, now sitting at -2.2 runs per 100 pitches. In baseball terms, that's a steep drop-off. It's like watching a reliable car suddenly start sputtering on the highway.

The Mariners seem to recognize the issue, too. Why else would they call for so few sinkers? In his prior start, Woo threw seven sinkers in the first two innings but only three over the rest of the game. The team sees the results, and they're not pretending the problem will magically fix itself.

Sure, the strategy to minimize the sinker worked on Wednesday—once. But as the old saying goes, band-aids don't fix bullet holes. One good start doesn't erase the underlying concern.

So what's gone wrong with the sinker? Sinkers aren't typically designed to generate whiffs, but Woo's is producing the lowest swing-and-miss rate of his career. Instead, the pitch is supposed to induce weak contact. By that measure, it's been a disaster. Over his first three seasons, Woo allowed an expected damage on contact (xwOBAcon) of .322. This year? That number has ballooned to .419. To put it in perspective, it's like turning a solid hitter into an MVP-caliber threat every time the ball is put in play.

The strangest part? The pitch shape itself hasn't changed much. The movement, the velocity—it all looks familiar. But the results tell a different story, and until Woo and the Mariners figure out why, I'll be watching with a cautious eye.