The Cardinals entered the season planning to work in rest for Miller, who is in his second full season as a Major League starter. This presented the most obvious opportunity to do that.
"How long that lasts, I'm not going to say [it will be through the end of] the month," Matheny said. "We'll see how guys look and feel. He's ready to go [in the bullpen]. As far as how we use him, it's how we need him."
The Cardinals will, however, revisit these plans, Matheny said, if Miller does not get any use out of the bullpen. The Cards want a reduced workload, not inactivity. There could be benefits to the mental break for Miller, too, as he labored to pitch deep into games and limit the walks in the first half. He has a 4.29 ERA and 1.47 WHIP through 19 starts (109 innings).
As for Wainwright, he will make his first second-half start Tuesday to open a two-game series against the Rays. That will be 10 days after his last start, not including the 21-pitch appearance he made in the All-Star Game this past Tuesday.
"I think they're just being real cautious of making sure that I'm going to be prepared to go the rest because this is going to be a pretty torrid race through the end of the season," Wainwright said. "I think they're mindful of that and they need me to be out there every fifth day. I don't need to be skipping starts. I feel very good, so I don't think I would have done that anyways."
Wainwright affirmed that he has felt no recurrence of discomfort in his forearm since skipping a start last month because of the issue. He entered Friday second in the National League with 138 innings.
"We've worked him hard, and plan on working him hard the rest of the way," Matheny said. "The schedule works out good to get a little extra time for him."
Jenifer Langosch is a reporter for MLB.com. Read her blog, By Gosh, It's Langosch, and follow her on Twitter @LangoschMLB. This story was not subject to the approval of Major League Baseball or its clubs.