The answer, of course, is all season, until you get a perfect in house replacement in AAA and a perfect in house replacement on the MLB roster. Only then is it okay to make any sort of a change. Rickie is 2nd in the league in walks. He's more likely to keep on doing that than Lucroy is to continue with a .370 BABIP. If they moved Lucroy up vs LHP, I could be okay with that, but he's been terrible in his career vs RHP, and he's been nothing special vs them so far this year (.704 OPS.... compared to a 1.210 OPS vs LHP) BABIP shows if a guy has been lucky or not. Players of a certain skill set may carry a higher BABIP than most people (usually fast, ground ball hitting lefties), but for the most part, players keep a remarkably consistent BABIP over their career. .370 season long babips by slow right handed catchers just don't happen.