George Springer isn't eligible for free agency for another two years, Carlos Correa three and Alex Bregman four. With the 28-year-old Jose Altuve locked into a long-term deal, the core of the Houston Astros, the best team in the AL West, will remain intact through 2020, at least.
The Oakland Athletics are built around young players as well, and if they actually break ground on their proposed ballpark, they would have more incentive to keep their best guys, rather than churn them out in trade. The state of the Los Angeles Angels' organization is improving, slowly, and they have Mike Trout, so they're always a few moves away.
The timing is exactly right, then, for the Seattle Mariners to tank or rebuild or whatever you want to call it. And by trading his best players, general manager Jerry Dipoto is well on his way to restocking what has been one of baseball's thinnest farm systems. Since the end of the World Series, Seattle has off-loaded catcher Mike Zunino, ace James Paxton, All-Star closer Edwin Diaz and Hall of Fame candidate Robinson Cano.