Appel was considered a possible top pick last year, but Houston passed on the hometown kid and instead chose 17-year-old shortstop Carlos Correa from Puerto Rico. Appel slid to Pittsburgh at No. 8 but turned down a $3.8 million offer and returned to Stanford for his senior season.
The move paid off for Appel, a hard-throwing righty with a fastball in the mid-90s (mph). After going 10-4 with a 2.12 ERA and 130 strikeouts in 106 1-3 innings this season for the Cardinal, the 6-foot-4, 195-pound Appel is expected to fetch about $2 million more than he passed on with the Pirates.
The deadline for teams to sign draft picks is July 12, but that doesn't apply to Appel because he is a college senior.
The draft, which is held over three days and 40 rounds, started Thursday night with the first two rounds at MLB Network Studios.
It was the second straight season that the first pick was uncertain going into the draft, with Oklahoma right-hander Jonathan Gray and a pair of college third basemen North Carolina's Colin Moran and San Diego's Kris Bryant thought to be in the mix for Houston.
It was the fourth time the Astros had the No. 1 pick, and they joined Tampa Bay (2007-08) and Washington (2009-10) as teams to have the top selection in consecutive years. The draft order is determined by reverse finish worst to best in the overall standings from last season.
With the No. 2 pick, the Chicago Cubs selected Bryant, who led Division I college players with 31 home runs this season. The 6-foot-5, 210-pound junior is a Golden Spikes finalist and Collegiate Baseball magazine's national player of year who also was leading the nation with 66 walks, 80 runs scored and an .820 slugging percentage.
Gray went third overall to the Colorado Rockies. The 6-foot-4, 245-pound flamethrower helped pitched the Sooners into the super regionals of the NCAA tournament, going 10-2 with a 1.59 ERA and 138 strikeouts in 119 innings. He throws a fastball in the mid- to upper-90s, reaching 100 mph at times with an effortless delivery.
Colorado apparently was not scared off by published reports that cited unidentified sources who said Gray tested positive for the medication Adderall during baseball's predraft drug testing program.