The Seattle Mariners traded two MLB Pipeline top-100 prospects over the winter, and both were expendable. Harry Ford was only ever going to back up Cal Raleigh, and Jurrangelo Cijntje was the club's third-best pitching prospect.
In fact, rumors of the Mariners being willing to trade Cijntje started percolating about a month before he actually went to the St. Louis Cardinals. The return was Brendan Donovan, who is doing everything in his power this spring to ensure Seattle won't get buyer's remorse.
Meanwhile, the Cardinals have pretty much committed to the same path the Mariners were going to take with Cijntje.