In response to Mets general manager Sandy Alderson’s question: That outfield. Of course, when Alderson wondered aloud “what outfield?” last November when asked about that unit, Collin Cowgill still played for Oakland and Marlon Byrd was heading to Mexico just hoping to revive his career. Yesterday that tandem might as well have been Mike Trout and Josh Hamilton carrying a lineup, helping the Mets continue their Opening Day dominance. With Cowgill and Byrd combining to drive in six runs and Jon Niese seizing the moment as Johan Santana’s replacement atop the rotation, the Mets stomped the Padres 11-2 before an announced sellout of 41,053 at Citi Field. It was their 10th victory in their last 14 openers and improved their overall Opening Day record to 34-18. Cowgill, who didn’t learn until Saturday he had won the job as the Mets’ starting center fielder, hit a grand slam against Brad Brach in the seventh inning and finished 2-for-5 with four RBIs. Byrd, Daniel Murphy, John Buck, Ruben Tejada and Niese were the other Mets with two hits. “Collin took the opportunity and ran with it, which is what we talked about all spring,” Terry Collins said. “I’m not sure I’ve been around a guy that competes like this guy does. It is max effort in practice, it is max effort in a game, and you just liked his energy.” It was Cowgill’s first career Opening Day start after serving as a backup in Oakland and Arizona the last two seasons. The Mets acquired him in December for infielder Jefry Marte, but envisioned him as a backup. That was until Alderson missed on attempts to add Justin Upton or Michael Bourn and no alternative emerged in spring training to seriously threaten Cowgill for playing time in center.