"I just thought it was a good time to throw it," Siegrist said. "I think the only way I'm going to get comfortable in those game situations is if I throw it in game situations."
It bounced near the lip of the grass for a ball. That was no deterrent for Siegrist, who went right back to the curve again. That time, it induced a swing-and-miss from the Rockies' cleanup hitter.
"Loved it," manager Mike Matheny said of the sequence. "I don't know if the camera caught us over here, but I jumped up and yelled and whistled as soon as the first one happened. I was happy to see it. That should have been very affirming to him when he sees one of the best left-handed hitters in the league approach that like he did."
Siegrist toyed with that curveball all spring, believing it could become an asset specifically against left-handed batters. He wondered if he had become too predictable with his heavy reliance on a fastball-changeup mix.
It hasn't been a pitch, however, that Siegrist had felt ready to use much in games. He threw two curveballs in an appearance against the Braves on April 10, but he had otherwise gone back to the pitch only once.
But the work has continued behind the scenes. Siegrist will throw a few curveballs during his daily long toss sessions and afterward ask his throwing partner, Tyler Lyons, to grade the spin. Through that exercise, Siegrist has been able to fine-tune his grip and release point.
"It's starting to feel a lot better," Siegrist said. "I just have to start throwing more of them now."
The possibility that Siegrist could develop another weapon should be a scary proposition for opponents, who are having enough trouble with him as he is. Entering Thursday with 25 strikeouts in 17 innings, Siegrist has fanned 38.5 percent of the batters he has faced, the second-highest percentage among National League relievers. Seventeen of those strikeouts have come over 9 1/3 innings of work at Busch Stadium.
"He worked so hard [on the curveball] in spring that I just didn't want to see him abandon it," Matheny said. "He just opened up that Pandora's Box with Yadi, too, by saying, 'OK, I want to throw this.' Now it's like having a whole new tool. Smart. It's really smart."
Jenifer Langosch has covered the Cardinals for MLB.com since 2012, and previously covered the Pirates from 2007-11. Read her blog, By Gosh, It's Langosch, follow her on Twitter @LangoschMLB, like her Facebook page Jenifer Langosch for Cardinals.com and listen to her podcast. This story was not subject to the approval of Major League Baseball or its clubs.