SAN FRANCISCO — When your postseason odds are listed as 0.7 percent in June, which is where the San Francisco Giants were listed Wednesday night, “there’s a lot of baseball to be played” turns from a hopeful phrase to a lamentation.Under those circumstances, irrelevant in the playoff picture with three months remaining on the schedule, it’s all too easy for a major-league roster to become a collection of extremely well compensated clock punchers.But there will be plenty at stake for the Giants over the next 83 games. There will be scads of opportunities for the front office to learn and evaluate. There will be growth opportunities for the rookies, stat-padding opportunities for arbitration-eligible players and plenty of game-management experience for a dugout boss, Tony Vitello, who began the season with no grounding in pro baseball. There will also be trade opportunities for some players that will expand with the blessings of health and an uptick in performance.From a business standpoint, every home game that remains is an opportunity for the Giants to sell a compelling and entertaining vision of a brighter tomorrow to fans who have shown up in robust numbers thus far but couldn’t be blamed if they’ve begun to lose confidence or interest or both.So under the circumstances, Wednesday night’s 2-1 victory over the Athletics on the shores of McCovey Cove represented a best-case scenario.The Giants activated right-hander Tyler Mahle from the Injured List and he exceeded their expectations, showing an uptick in stuff, taking a shutout into the sixth inning and likely putting himself on the list of acquisition possibilities for several contending clubs. That could allow the Giants to escape the remainder of his $10 million salary and get a prospect or two in return.They played an aesthetically clean and crowd-pleasing game against their Northern California rivals, with Jung Hoo Lee making a pair of difficult catches in right field, including one that stranded two runners in the ninth inning, and Victor Bericoto showing off a strong arm to throw out a runner at the plate on a bizarre play to end the fifth.As for punching that clock? They got that done with dramatic flair in the ninth. Rafael Devers, who fouled off a half-dozen center-cut pitches in his first three at-bats, connected against right-hander Elvis Alvarado for a tying home run that slipped over the center field fence to start the inning. Then with two outs, Bericoto, a 24-year-old rookie who lacked prospect sheen as he moved up the organizational ladder and had to earn every chance he’s gotten, hammered a pitch over the wall in left-center for the first walk-off hit of his career.