PITTSBURGH — The Pittsburgh Pirates had a promising start to the season and were one of baseball's most surprising teams, but a recent skid threatens to ruin all the progress they've made over the first month of the season. The Pirates have lost five straight games, which includes suffering a four-game sweep to the St. Louis Cardinals at PNC Park, April 27-30, where they allowed double-digit run totals twice and got outscored 30-18. Pittsburgh now sits .500, 16-16 overall, and last in the highly competitive National League Central Division, of which they've already played four series against so far. The Pirates will also host their biggest rival in the Cincinnati Reds this weekend, who are 20-11 and top of the division, which means they have to get back to winning ways sooner rather than later. What's Gone Wrong For the Pirates The Pirates' longest losing streak prior to this was just two games in the first two games of the season vs. the New York Mets at Citi Field, March 26 and March 28.…