The Houston Astros' rotation has struggled to produce and stay healthy this season, and Mike Burrows is no exception. When the Astros acquired Burrows last offseason in exchange for two prospects, the expectation was that he'd make an immediate impact in the rotation. He certainly has made an immediate impact, but not in the direction Houston hoped. The righty allowed seven runs in 5.2 innings on Thursday afternoon in the Astros' loss to the Seattle Mariners. His ERA has ballooned up to 5.72 through nine starts, and he's recorded just two quality starts this season. Everything was trending in the right direction after his previous three starts. He allowed just five runs over 18 innings, including a three-hit seven-inning shutout of the Cincinnati Reds last week. Despite the momentum , things have swung in the opposite direction in a hurry. Diving deeper, Burrows has struggled primarily with two pitches: his four-seamer and slider.…