Castro made two throwing errors on Saturday in the Cubs' 5-1 loss the Cardinals. The first one might have been a result of Castro hurrying his throw because of the runner, and the second one was more a mechanical flaw.
"Sometimes you're going to have those errors," Sveum said. "It's still part of the process."
Castro is on a good pace on both offense and baserunning so far. His six steals were the most the Major Leagues entering Sunday's action, and he is one of 14 Cubs to record at least six stolen bases in April since 1921.
Sveum has tried to get the Cubs to be more aggressive on the basepaths. So far, they've swiped eight bases in nine games. Last year, the Cubs did not record their eighth stolen base until May 17, which was Game No. 40.