After Angel Pagan struck out, Scutaro lined a pitch into center field that fell in front of Austin Jackson and Theriot easily beat the throw home.
Sergio Romo struck out the side in the bottom of the 1inning for the save and the Giants claimed their second world championship in three years with a dominating 4-0 sweep of American League champion Tigers.
Buster Posey socked a two-run homer and Brandon Belt contributed an RBI triple for San Francisco.
Santiago Casilla was credited with the decision that earned the Giants the seventh world championship in their 129-year history.
2014: The Year in Fashion [PHOTOS]
LeBron James reveals his new Nike shoes