As far as omens go, Franklin Gutierrez hitting a home run in his first at-bat after coming off the 60-day disabled list is a promising one. And, sure enough, it set into motion one of the most exhilarating games of the season for the Mariners as they pulled out a 7-5 victory over the A’s. Down by three runs in the seventh and staring at their fourth straight loss, they tied it on Raul Ibanez’s three-run homer, then stormed into the lead on a two-run single by Nick Franklin in the eighth. It was a triumph fueled by the team’s most grizzled and respected veteran in Ibanez, and the rookie who has earned his growing admiration. “Just more proof,’’ Ibanez said of Franklin’s big one-out hit. “He has a great approach at the plate, and he doesn’t try to do too much. He has a really good eye. He’s a very disciplined hitter.” And one who is already showing that he embraces the big moment. “I think you’re a better baseball player when you play with no fear, and we’ve seen that from Nick so far,’’ Mariners manager Eric Wedge said. Franklin, in turn, marveled at Ibanez’s clutch hit that sent the comeback into motion. “Right when he came up,’’ he said, “you get one of those feelings, and when he does it, you say, ‘How does he do it?’ You’re not even excited. You just shake your head, like, wow.” Yoervis Medina, who had entered the game in the seventh and promptly gave up two run-scoring singles, finished off the A’s in the ninth for his second victory. He gave up a leadoff single to Jed Lowrie but induced a double-play grounder from dangerous Yoenis Cespedes, well-turned by Kyle Seager and Franklin. On a beautiful summer night, the portion of the crowd of 20,704 rooting for the Mariners initially had little to make them happy besides Gutierrez’s homer and a lovely sunset behind Safeco Field.