He started a bit slow, but by the time Mulder's 30-pitch session had ended, he was excited about how he was throwing. Mulder mixed in a full assortment of fastballs and offspeed offerings during the course of 10 simulated plate appearances.
"I came away very happy with it, especially the way I ended," Mulder said. "If I would have thrown all of them the way I started, those first 10 or 15, I probably wouldn't have been real happy with it. But the way I felt at the end, I was pleased with that."
Mulder threw to a group of three Minor League hitters: Allen Craig, Daniel Descalso and Oliver Marmol. The players took simulated at-bats, totaling one walk and one "base hit" on the empty field. Mulder broke one hitter's bat and threw approximately 16 to 18 of his pitches for strikes.
Early in the session, Mulder left many of his pitches up. He missed high with his fastball and didn't get good action on his curveball. After the 15-pitch mark, though, he got his pitches down and his stuff got sharper.
Mulder broke Marmol's bat on a popup, and also got the infielder to dive after a pitch that dove viciously down and out of the strike zone. Eleven of Mulder's final 16 pitches went for strikes.
"Everything doesn't work as smoothly when I'm loosening up and playing catch, but once I start to get into the flow of it, it starts to move quicker," Mulder said. "But where we're at right now, we're just finishing up when I'm starting to feel good.
"The first 15 pitches, it was tough for me to get loose, and the last 15 I was much more pleased with. We were debating whether to stop in between 15, and I'm glad I didn't. Because it would have been harder for me to get going."
Mulder underwent left shoulder surgery in September, his second operation on the joint in a little more than a year. He has been gradually building up his workload, throwing bullpen sessions since early in spring. On Saturday, however, he took a significant step forward.
"I feel strong," Mulder said. "There's a different strong when you get on the mound and you've got to go innings and the competitive juices start flowing. That's a little different. But I was very pleased with the way I felt [Saturday]."
Manager Tony La Russa, pitching coach Dave Duncan and bullpen coach Marty Mason watched Mulder, as did general manager John Mozeliak, assistant general manager John Abbamondi, members of the Cardinals' scouting department and pitchers Chris Carpenter and Jason Isringhausen.
"I thought from the beginning, when you put everything together, he was outstanding," La Russa said. "He made a bunch of good throws."
Mulder will likely throw to hitters again in three days. He is still probably several throws away from getting into a game, but he has encountered no setbacks in his rehabilitation process. The club's target date for him has been sometime in May, and nothing has occurred to change that plan.
"I haven't had any days where I came away hurting or real sore or anything like that," he said. "I've just had days where my arm didn't just flop back. I'd say it's some of those bad habits, but it's more just that I couldn't trust it that day. It's nothing bad. It's just not something you want to continue to keep doing."
Matthew Leach is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.