BRADENTON, Fla. -- The Pirates have two top prospects widely expected to crack Pittsburgh's rotation at some point this summer: Tyler Glasnow and Jameson Taillon.

But the Bucs' future rotation options stretch beyond those two recognizable names, and manager Clint Hurdle suggested that depth may have played into the Pirates' offseason moves. While fans clamored for Pittsburgh to add another starter, or a more proven arm, the Pirates are likely going to open the year with Gerrit Cole, Francisco Liriano, Jon Niese, Jeff Locke and Ryan Vogelsong.

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Over the last year, several of the Pirates' top Triple-A arms have been sidelined with serious injuries. Nick Kingham is still recovering from Tommy John surgery, as are Casey Sadler and Brandon Cumpton. But a few arms have emerged to fill that void, specifically Chad Kuhl, Steven Brault and Trevor Williams.

"We do have depth, and it's real," Hurdle said. "I think one of the reasons that we've worked through our offseason as we have is knowing that there's Taillon getting better, there's Glasnow getting better, there's Chad Kuhl getting better."

Kuhl, Brault and Williams figure to be a part of Triple-A Indianapolis' starting rotation. Kuhl, a 23-year-old ground-ball machine, went 11-5 with a 2.48 ERA last season for Double-A Altoona.

The Pirates acquired Brault, 23, in the Travis Snider trade last offseason. He split the year between Class A Advanced Bradenton and Altoona, finishing 13-4 with a 2.43 ERA. The Bucs picked up Williams from the Marlins in November. Williams, 23, owns a career 3.35 ERA in the Minors and advanced to Triple-A last season.

"We definitely feel good about the progression of our guys putting themselves in place to be the next tier when needed," Hurdle said.

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Around the horn

• Triple-A Indianapolis pitching coach Stan Kyles interviewed this offseason for the D-backs' open bullpen coach job. Arizona wound up hiring Garvin Alston, a former Rockies pitcher.

The D-backs' interest in Kyles is yet another example of the Pirates' staff attracting interest from other organizations. This offseason, they saw two special assistants -- Marc DelPiano and Jim Benedict -- leave to take jobs in the Marlins' front office; Tyrone Brooks leave for a job with Major League Baseball; and third-base coach Rick Sofield interview for the Padres' managerial job.

• Position players continue to roll into Pirate City ahead of their scheduled Monday report date. Infielder Josh Harrison and first baseman Josh Bell joined the group on Saturday, as did newly signed outfielder Matt Joyce.

• Thirteen pitchers threw in the bullpen on Saturday. At one point, three-fifths of the Pirates' likely Opening Day rotation -- Vogelsong, Niese and Liriano -- were lined up alongside each other.