Westburg is getting more playing time at 2B and he's not really a platoon candidate, that I can see. His OPS vs. RHP is .694 and against LHP .699. He should be playing more based on his defense alone, but he's not hitting much more than Frazier right now, so there is no clear offensive upgrade.
His OPS was .928 in June, .676 in July, .670 in August, and .696 on the season. There is absolutely no guarantee that he's going to get better with more ABs this season, he's actually trended downward, which isn't unexpected, he'll have to adjust as the pitchers have adjusted to him.