Fontana, 25, long rated as one of Houston’s top prospects but has seen his stock decline steadily in recent seasons. Baseball America rated him 29th among Astros farmhands last winter, and by midseason, he’d fallen off MLB.com’s top 30 Astros prospects entirely. The former second-round pick batted a combined .203/.282/.273 in 451 plate appearances between Double-A and Triple-A this year. While the ’Stros once hoped that he could eventually man an up-the-middle infield spot, BA noted last winter that his ceiling now looked to be a utility infielder who draws plenty of walks but has bottom-of-the-scale power. BA did note that Fontana is a reliable defender at second base, even if he lacks the range or arm to handle shortstop on a regular basis. Fontana did hit .241/.369/.357 in a full season at Triple-A in 2015, so he does at least have a history of somewhat better performance at that level.
Graterol, 27, made his Major League debut and tallied 15 PAs with the Halos this past season. The former Royals farmhand spent the 2015 season in the Yankees organization before inking a minors pact with the Halos last offseason. He’s a career .274/.306/.338 hitter in parts of three seasons (95 games) at the Triple-A level.