The second game of what Argentines are calling the “trilogy” of Superclasicos between Boca Juniors and River Plate, the hated rivals of Buenos Aires, begins on Thursday night atRiver’s Monumental Stadium in the first leg of the Copa Libertadores round of 16. Boca won game one of the trilogy, 2-0, at La Bombonera on Sunday night in the Argentine league, a result whichhelped the South Buenos Aires club move three points ahead of Marcelo Gallardo’s team. The return leg of the Copa series will be at La Bombonera on May 14, capping the rivals’ thirdmeeting in 12 days.