"I was just trying to do what they're trying to establish here, just working quick and trying to get ground balls," Rosenbaum said. "I made good pitches, and my curve ball was down."
Four of his six outs were on the ground, and he's feeling good about his progress, working with pitching coach Jim Wright and assistant pitching coach Bo McLaughlin on refining his mechanics.
The big challenge could be if the Rockies see him as a better fit in the bullpen than in the rotation. As a Rule 5 player, the Rockies could lose him for $25,000 to his old club, the Nationals, if he's not on the Opening Day roster.
"I've started my whole career," the 25-year-old left-hander said. "It's going to be different coming out of the 'pen, but I got to [relieve in the instructional league] a couple times. It's pitching, so it's the same game."
Chris Volstad followed Rosenbaum on Friday, pitching three innings and allowing one run on two hits, elevating his spring ERA to 1.80.
"I've been working on pounding the bottom of the zone, especially that sinker," said the 6-foot-8 right-hander. "I felt good with that. I threw good changeups. The curve ball still needed a little bit of work. I'm trying to get a better feel on that. But overall, a good outing. I'll take that."
Volstad has played parts of five seasons in the Majors, four with Florida and last year with the Cubs. He was with the Royals for a month in the offseason before signing a Minor League contract with the Rockies and coming to camp as a non-roster invitee. He sees himself squarely in the fifth-starter mix, easily the most competitive battle the Rockies entertain this spring, with at least a half-dozen viable contenders.
"That's what I need to tell myself, whether it's true or not," Volstad said of his presence in the thick of the competition. "Whether if other people believe it, I don't know, but I'm definitely telling myself that and going out there and trying to prove that."
He has at least one believer where it counts in manager Walt Weiss.
"That's why we brought him in, to compete for that spot," Weiss said of Volstad's standing. "His strength is he's able to sink the ball. He's got to be at the bottom of the zone with that sinker. If he can do that he'll be effective, because he'll get a lot of groundballs. He's got heavy sink."