In return, the Phillies acquired four prospects, according to multiple media reports. Right-hander Vincent Velasquez, left-hander Brett Oberholtzer, outfielder Derek Fisher, and one yet to be reported player head to Philadelphia for Giles.
The Astros have wanted to get a hard-throwing relief pitcher for quite some time now, considering the back-end of their bullpen was fairly weak in 2015. Names that had been mentioned as targets for Houston included Aroldis Chapman, Craig Kimbrel, and others.
Giles appears to be their man, though. He throws 100+ MPH and has had two stellar seasons in Philadelphia. After coming up midway through the 2014 season, Giles was promoted to Jonathan Papelbon's setup man, a position he held until Papelbon was traded to the Nationals this past July.
From July 24 on, Giles had 17 save situations and saved 15 of them. He was groomed to be a closer and succeeded well in his brief time there. In Houston, he will trump Luke Gregerson in the full-time closing spot.
Overall, Giles went 6-3 with a 1.80 ERA (2.13 FIP) in 69 appearances. Over his 70 innings pitched, he struck out 87 guys and walked just 25. Giles' command with both his fastball and slider has allowed him to be effective in a back-end relief role with Philadelphia.
Giles also comes with plenty of team control. Being so good, so young, Giles is still signed through the 2020 season through the pre-arbitration and arbitration processes. This increased his value for Houston, as Giles will not only be the closer now, but he will be for a long time.
Houston had to give up a lot of talent in order to acquire Giles. Velasquez was rated as the 86th-best prospect in baseball (via MLB Pipeline) prior to the 2015 season and Fisher was their 1st round pick in 2014. In order to get Giles, they truly had to pay the price.