"I haven't talked to him yet, but I will talk to him," Sveum said Wednesday. "There was a lot of shaking off going on. We'll try to get to the bottom of it."
Volstad took the loss Tuesday, giving up six runs over 4 1/3 innings. He is now winless in his last 20 starts.
"It seems like the same old thing with Chris," Cubs pitching coach Chris Bosio said. "He puts up four or five zeros, and then he starts pressing a little bit."
Volstad gave up one run on three hits over the first four innings, but the first two batters in the fifth each singled, and then he walked pinch-hitter Chris Hinske. Then, it snowballed.
"He said he tried to make a perfect pitch [to Hinske], and he didn't," Bosio said. "He threw some good pitches, and he threw some other pitches that were questionable in certain counts. His tempo was good, and he battled. ... There's still a lot of improvement that needs to happen with Chris, and not only mentally, but physically."
Sveum was upset after the game that Volstad didn't follow their game plan.
"I'll just say we wandered a little bit from what we want to do," Bosio said.
The Cubs have asked their catchers to take an active role with the pitchers.
"We do have a clear game plan, and when we execute our plan, for the most part, we've been in every game," Bosio said. "It's when we deviate or walk guys or don't make pitches [that get us in trouble]. That walk yesterday really hurt us in that inning. A pinch-hitter coming off the bench, a guy like Hinske, will give him a professional at-bat. That was a huge spot there where we needed him to put the ball in play, and we weren't able to do it."
Catcher Steve Clevenger, who was behind the plate Tuesday, must have felt like Crash Davis from the movie "Bull Durham." The rookie was behind the plate Monday and guided Jeff Samardzija through seven solid innings in which he gave up one run and struck out a career-high 11 batters against the Braves.