"He has all the ingredients you look for in a young pitcher -- size, arm, stuff," executive vice president of baseball operations Dan Duquette said of Rodriguez. "And he has the results, also."
The 6-foot-4, 200-pound Rodriguez pitched in the SiriusXM All-Star Futures Game last year and was named to the Eastern League All-Star team. He was the Phillies 17th-best prospect in 2011, according to Baseball America.
Welty, 25, hit .333 with 13 homers and 55 RBIs in 213 at-bats over four levels last year, maxing out at Double-A, where he hit .286 in 37 games.
Brittany Ghiroli is a reporter for MLB.com. Read her blog, Britt's Bird Watch, and follow her on Twitter @britt_ghiroli. This story was not subject to the approval of Major League Baseball or its clubs.