#3 Hunter Harvey
Hunter Harvey has quietly been one of the better relievers in baseball over the last two years. In 95 appearances for the Nationals, Harvey has thrown 100 innings, posting a 2.70 ERA, 1.02 WHIP and 2.81 FIP. His fastball velocity is in the 97th percentile, he limits walks with a 5.5% walk rate, and strikes out opposing hitters at a 28.5% clip.
It's no secret the Astros have to rebuild their bullpen after the losses of Hector Neris, Phil Maton and Ryne Stanek. Harvey actually has some similarities to Stanek as a flame-throwing righty, but unlike Stanek, he allows virtually no walks.
Harvey would come with two years of team control, not quite fitting the Nationals window of when their young talent will be ready to contend. A player of Jake Meyers caliber could easily head to Washington in exchange of Harvey, giving the Astros a filthy three-headed monster in the back of the pen with Harvey, Abreu, and Pressly.