PITTSBURGH — The calendar has flipped to May, and the Pittsburgh Pirates stand at the most maddening non-losing record in baseball: 16-16. It's the high-water mark of mediocrity, a number that perfectly encapsulates a month of dizzying highs, a genuine pulse, and a current five-game losing streak that has the fanbase reaching for the antacids. Through the first few weeks of the season, the Pirates looked the part of a legitimate contender. The starting pitching was dominant, the offense had a thunderous middle, and PNC Park felt like it was shaking off two decades of irrelevance. Now, stumbling into May on a five-game skid, the cracks beginning to show are impossible to ignore. In the most competitive division in baseball, the Pirates have little margin for error. But so far, it's the little "things" that have mostly held them back from a winning record. Chiefly, good defense and late game execution.…