"Pitching should be competitive next year," Towers said. "I'm hoping that guys like Stites and Jake Barrett push some of the guys in our bullpen next year too."
Barrett was the team's third-round pick in the 2012 First-Year Player Draft out of Arizona State University.
The 22-year-old compiled a 0.36 ERA (one earned run in 24 2/3 innings) after being promoted from Class A Visalia to Double-A Mobile. Barrett will get a chance to improve his stock even more in the Arizona Fall League this year.
So will Stites, who was acquired from the Padres in the Ian Kennedy deal. The 23-year-old has not pitched in the Arizona system since the trade due to an appendectomy.
Steve Gilbert is a reporter for MLB.com. Read his blog, Inside the D-backs, and follow him on Twitter @SteveGilbertMLB. This story was not subject to the approval of Major League Baseball or its clubs.