"It's a hard decision. You've got a guy [Vogelsong] that's got experience," Hurdle said. "I told Ryan this wasn't about him not performing well. He came to Spring Training and tracked things out that he wanted to do.
"It was about another guy pitching the most effective we've ever seen him pitch and trying to leverage that opportunity for him. This might be a window of opportunity for Juan Nicasio to get back into play."
Nicasio will start the Pirates' third game of the season against the Cardinals, following left-handers Francisco Liriano and Jonathon Niese in the rotation.
Nicasio signed a one-year, $3 million deal with the Pirates in early December after a year spent mostly in the Dodgers' bullpen. Formerly a starter with the Rockies, Nicasio has thrived this spring by taking his reliever's mentality into an expanded role.
"One of the things we've talked with him about is just staying focused in the moment. It's just one pitch at a time," Hurdle said. "When that hitter's done, then it's just the next hitter. It's not five innings. It's not six innings. ... Now, how does that go into the season? Now, he's going to get that opportunity."
Nicasio's breakthrough became apparent on March 16 against the Orioles, when he struck out 10 of the 14 batters he faced over four innings at Ed Smith Stadium. He located his fastball well and wiped out hitters with a nasty slider, mixing in the occasional changeup to keep them off-balance.
Afterward, Hurdle called it the the kind of start that "will get your attention." The Pirates entered camp committed to stretching out Nicasio like a starter, but there appeared to be no opening in their five-man rotation.
As Nicasio neared the end of his lights-out spring, consistently showing the pure stuff the Pirates always knew he had, they created room by moving Vogelsong to the bullpen.
Vogelsong will assume the multi-inning role that had seemingly been designated for Nicasio. The 38-year-old Vogelsong struggled out of the Giants' bullpen last season, posting a 5.68 ERA over 11 appearances.
The right-hander struggled to put away hitters in his last Spring Training start, giving up six runs (five earned) on nine hits and two walks over 4 1/3 innings against the Red Sox on Friday.
Vogelsong will pitch in relief in the Pirates' Grapefruit League finale on Thursday.
"He was completely professional, disappointed absolutely. You'd want him to be. He poured everything into that, and that was one of his goals coming in," Hurdle said. "I do think he'll have every opportunity to show the experience he's got and the competitive nature that he's got to do well for us out there."