Game 2 of the doubleheader! It’s a great day for a ballgame; let’s play two! The A’s are doing just that against the Angels on Saturday at the Coliseum, and Oakland won the first game in dramatic fashion. Trailing by two runs in the bottom of the 9th, with two out, rookie Luis Barrera hit a three-run walk-off homer, his first career dinger. Last-minute comeback! They’ll ride that momentum into the nightcap, with rookie pitcher Adam Oller on the mound. The right-hander was called up specially for this occasion, as the 27th man for the doubleheader, and he’ll return to…