First start at AT&T Park special for A's Semien

7/8/15: Marcus Semien rips a two-run home run into the left-field seats to get the A's within a run in the 9th inningSAN FRANCISCO -- As a kid, Marcus Semien often came to Giants games with his grandmother, Carol Phillips, and dreamed of one day playing a Major League game inside the stadium.

On Saturday, the A's shortstop got that chance, making his first professional start at AT&T Park and batting leadoff.

"There's nothing like being on the field as a player," Semien said. "You couldn't ask for anything more."

Semien played at the park in college when he shined at University of California-Berkeley, in exhibition games earlier this season and Friday night, when he pinch-hit, so it's something…