The Red Sox scored one of the biggest coups at the non-waiver trade deadline Tuesday, acquiring right-hander Eric Gagne from the Rangers. Gagne, 31, waived his no-trade clause to Boston in exchange for financial considerations. The Red Sox also assured Gagne that he will close games on nights that Jonathan Papelbon is unavailable. In return for Gagne, the Rangers received left-hander Kason Gabbard, Class AAA center fielder David Murphy and Class A outfielder Engel Beltre, sources say. Beltre is just 17 years old. Before reaching agreement with the Red Sox, the Rangers had discussed trading Gagne to the Mets, Yankees and Brewers. He could have been sent to each of those teams without his permission.