There isn't a pattern either.
"Every error has been a different kind of error, too, whether it's throwing to first, throwing to second, a little dribbler to the mound," Sveum said. "We've thrown some balls into center field. Between the errors by pitchers and [being] second in the National League in walks and hit batters, that just adds up to way too many people on base. And the bottom line, like I keep saying, is when we make that mistake, we cannot seem to make a pitch after that."
That happened on Friday, as Jeff Samardzija's fielding error led to two runs by the Nationals in a 7-3 loss.
So, if the Cubs do the drills, why are they making the mistakes?
"It's hard [to explain], because we have really good athletes who are pitching," Sveum said. "We're not dealing with guys struggling with their athleticism. Hopefully, it's over with and that's the last we're going to see.
"Sometimes, the players just have to be able to perform in these situations. If you're a big league player, you have to be able to perform on the stage. It's like taking [batting practice] and ground balls; you can do that all day long and never make an error, but you have to be able to do it in games."
Carrie Muskat is a reporter for MLB.com. She writes a blog, Muskat Ramblings, and you can follow her on Twitter @CarrieMuskat. This story was not subject to the approval of Major League Baseball or its clubs.