De Los Santos is a 21-year old right-hander who made 24 starts and two relief appearances with San Antonio last season and finished the season 10-6 with a 3.78 ERA. He struck out 138 batters in 150 innings of work at Double-A. In three minor league seasons, De Los Santos is a combined 24-11 with a 3.70 ERA.
The Seattle Mariners singed De Los Santos as an international free agent in 2014 and he pitched in both rookie ball and Low-A ball in 2015. After the season, Seattle dealt him to San Diego along with infielder Nelson Ward for former Phillies reliever Joaquin Benoit. De Los Santos pitched in both A-ball and High-A ball in 2016 before spending all of last season at Double-A.
Galvis, who is eligible to be a free agent following the 2018 season, had spent his entire career with the Phillies after being signed as an amateur free agent in July of 2006. He played in all 162 games with the Phillies this past season and produced a slash line of 12-61-.255/.309/.382 and was a finalist for a Gold Glove Award, which was eventually awarded to Brandon Crawford of the San Francisco Giants. In 642 games with the Phillies, Galvis was a career .245 hitter with a .287 on-base percentage.
The move opens a spot for J.P. Crawford to take over at shortstop. Crawford made his MLB debut last season and hit .214 in 23 games – 87 plate appearances – with the Phillies. Galvis has also played at second and at third at both Triple-A and with the Phillies. It was likely that either Galvis or second baseman Cesar Hernandez would be dealt during the offseason as the Phillies looked to make room for Crawford. They also have Scott Kingery, a second base prospect, who may reach the majors at some point during 2018 after splitting last season between Reading and Lehigh Valley.