DETROIT — The tension palpable for almost four hours Wednesday night at Comerica Park could be explained by one word, uttered by Tigers Manager Jim Leyland before the game. A reporter asked him if various relievers would be available. “Postseason,” Leyland snarled. That’s all he needed to say. The Detroit Tigers and Texas Rangers played 10 innings of desperate, classic baseball Wednesday night, until the 11th inning arrived and closer Jose Valverde fell off the high wire he treads so expertly.