When the season began, it wasn't crazy to think that the A's could be leading the AL West after the first month of the season, holding a 17-14 record. The formula would be simple: Nick Kurtz is crushing baseballs just like he did in his rookie campaign, Brent Rooker would be the glue in the lineup, and Shea Langeliers would potentially take another step forward. Throw in guys like Jacob Wilson, who hit .311 last season, and Tyler Soderstrom, who led the A's in RBI last season, and you have a capable group of mashers that can get hot for a stretch. While some of that is true — in particular the bit about Langeliers taking another step forward — the reason for the team's success has been mostly about guys stepping up when given an opportunity, and the team getting a roughly league-average performance from the pitching staff. A's pitchers have combined for a 4.23 ERA through April 30, ranking them 17th in MLB. Last year they were either at, or near the bottom of those rankings the entire season.…