Appel, the No. 1 overall pick out of Stanford University in the 2013 First-Year Player Draft, went 10-3 with a 4.37 ERA in 25 starts last season between Corpus Christi and triple-A Fresno. Standing at 6 foot 5, 220 pounds, Appel struck out 110 batters in 131.2 innings and was named to the U.S. Team in the 2015 MLB Futures Game. The 24-year-old also led the Grizzlies to their first Pacific Coast League championship in franchise history, striking out 10 in a decisive Game 5 victory over Round Rock. Entering the 2015 season, Appel was ranked as the No. 2 prospect in the Astros organization and 31st in all of baseball by Baseball America. In 54 career minor league games (53 starts), the Houston, Texas, native is 16-11 with a 5.12 ERA and 221 strikeouts in 253.0 innings.
A native of Christiana, Del., Oberholtzer made eight starts for the Astros in 2015 and went 2-2 with a 4.46 ERA. In seven of those eight starts, however, the 26-year-old posted a 3.16 ERA, allowing six earned runs in only 1.1 innings in the other start. Oberholtzer also made 12 starts for Fresno, going 7-4 with a 3.86 ERA and in similar fashion compiled a 2.31 ERA in 10 of those 12 minor league starts. He was originally selected in the eighth round of the 2008 draft by the Atlanta Braves.
Selected by Houston in the second round of the 2015 draft out of Cal State Fullerton, Eshelman pitched last season with the Gulf Coast League Astros and Quad Cities, making two starts for each team. The 21-year-old pitched 10.1 innings in those four starts.
Harold Arauz, 20, is 11-8 with a 3.54 ERA over 53 career minor league games (34 starts). Over his four-year career, he has posted a 3.42 strikeout-to-walk ratio (178 SO, 52 BB) while averaging 8.64 strikeouts per 9.0 innings pitched. A native of Chiriquí, Panama, Arauz was signed by the Astros as an amateur free agent in 2011.
Giles went 6-3 with a 1.80 ERA and 15 saves in 69 games for the Phillies in 2015. The 25-year-old had 87 strikeouts in 70.0 innings and held opposing hitters to a .219 batting average. He was selected by the Phillies in the seventh round of the 2011 draft.
Jonathan Arauz, 17, batted .254 with 10 doubles, two triples, two home runs and 18 RBI in 44 games for the Gulf Coast League Phillies last season. He was signed by Philadelphia as an amateur free agent in 2014 out of Alanje, Panama.
To make room for Velasquez and Oberholtzer on the 40-man roster, the Phillies designated right-hander Dan Otero for assignment. Otero had been claimed off waivers by the Phillies from the Oakland A's on November 3.