It could prove to be a practical tune-up for what the Yankees hope is a long postseason run. For guys like Paxton, who has never pitched in the playoffs, it’s a chance to feel what it’s like to block out the electric atmosphere of a sold out ballpark that is excited and loud. Like Paxton, Sunday night’s starter, Domingo German has never appeared in a playoff game. He responded well to the playoff-like atmosphere in a big Sunday night game against the Red Sox at Fenway last month. Sunday night, going against Clayton Kershaw, the two pitchers who lead the majors in wins, was another chance for German to prove himself ready for October.