Sano is still striking out in 37.5% of his PA in 2019. Per 600 PA, Sano has averaged about 2.4 fWAR per 600 PA. Even neutralizing defense and position, it's only 3.0 WAR per 600 PA. His "rising" is a nice HR binge, which has value (up to 4.1 fWAR per 600 PA at his 2019 rates), but it's not really comparable value to a once and potential future ace, is it? Syndergaard has averaged 5.0 fWAR per 31 starts in his career. Even in his "down" year of 2019, he's accumulating fWAR on par with Sano's "rising" 2019 -- 4.2 pace. And in terms of health, Syndergaard's missed time is mostly concentrated in one season (2017). Sano hasn't managed a full season since 2015. That's going to affect projections. Furthermore, there are still real questions about Sano at 3B -- especially on an NL team (no DH spot available) with 1B blocked. If Sano had 4+ years of control, maybe I could squint and see it. But at 2 years of control, I can't see why the Mets would be interested in this exchange, without significant other pieces (on the level of Lewis or Kirilloff).