With the score at 1-1, Ramirez let an Aramis Ramirez hit get past him, allowing the Cubs third baseman to reach third with nobody out. He would later score on a Kosuke Fukudome double to give the Cubs a lead they would never relinquish, eventually winning 3-1.
Earlier in the game, Ramirez bobbled a bloop single, allowing runners to advance an extra base.
"It's a long season and that's going to happen," Ramirez, who went 0-for-4 at the plate, told The Associated Press. "We're trying to hold the lead. We won three out of four against Chicago, so it's good. We've got to keep going and try to beat everyone."
The loss, combined with a Rockies win, shrunk the Dodgers' lead in the NL West to 3 1/2 games.