Even while continuing to sell his plan for rebuilding, Chicago Cubs president Theo Epstein admits to mistakes over the course of his first two years in charge. Although the Cubs have been able to acquire talent throughout the organization over the past two seasons, Epstein says he hasn't provided the best atmosphere at the major league level for development. "I haven't done a good job at that," he said to a room full of season-ticket holders at the Bank of America Theatre on Friday. Epstein believes he's fixed that problem with Thursday's hiring of San Diego Padres bench coach Rick Renteria, who replaces Dale Sveum as manager. The biggest missteps have come in the handling of the offense and specifically his shortstop, Starlin Castro. The Cubs ranked 14th in on-base percentage -- an admitted critical category -- in the National League while Castro hit .245, the lowest of his career. "That's one area where we had mixed messages," Epstein said. "We had players being pulled in a couple different directions." That might not bode well for the return of hitting coach James Rowson or his assistant, Rob Deer. And it may have helped cost Sveum his job. Epstein said the Cubs will make coaching decisions in the coming days, and hitting coach will be an important one.