Mujica, who has converted 31 of 33 save opportunities this season, said his arm felt tired after throwing 24 pitches in a two-inning relief appearance on Thursday. It was the third straight two-inning outing Mujica had made, and he threw 71 pitches during that five-day span.
"I was tired," Mujica said. "I talked to [Matheny], we have good communication. I said, 'Mike, I feel, not sore, but just a little tired.' I prepare for one inning, maybe four or five outs, but to have two innings three times in a row [was a change]. It was good to have these three days [off]."
Both Mujica and Matheny were optimistic that Mujica would feel fresh enough to pitch, if needed, on Monday in Milwaukee. Matheny also explained that he didn't divulge the information earlier for the sake of competitive advantage. Matheny was asked Sunday morning if Mujica was available Saturday and answered in the affirmative.
The Cardinals' bullpen as a whole was able to reset during this three-game series, which should free up other restrictions Matheny has had lately in how to use his relievers.
The 'pen entered the weekend series in Chicago having thrown 16 2/3 innings in three games against the Pirates. The Cardinals didn't need to use any reliever more than once over the last three days. Rosenthal is among those who seemingly could benefit most from any opportunity for rest.
In his first full season as a reliever, the rookie Rosenthal ranks first among Cardinals relievers in appearances (56) and innings pitched (58 2/3) after Sunday's scoreless ninth. He is on pace to pitch in 74 games, a total reached by a Cardinals reliever only three times since 2009.
As the Cardinals look to find ways to spell both Rosenthal and Mujica, Michael Wacha's presence could become crucial. The rookie right-hander has struck out seven of the nine batters he has faced in three perfect innings of relief.
"He was pretty impressive, came in and did a nice job," Matheny said of Wacha's outing Saturday. "We knew we had to get him exposed at some point to some higher-leverage situations, and that was nice to get him in there and get us some big outs, more than anything else."
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.