He finished the night as Fox's Player of the Game after going four for five with three runs batted in and two runs scored.
Sanchez, a former National League batting champion, doubled in his first three series at-bats against Texas starting pitcher Cliff Lee, who came in 7-0 in eight career postseason starts. Sanchez became the first player in World Series history to hit three doubles in his first three series at-bats.
"I didn't know it was a record," Sanchez said in a postgame television interview. "It didn't cross my mind.
"I'm just glad I was able to help the team today and get some runs across and help the team most of all."
He also had a run-scoring single and scored two runs for the Giants, who finished with 14 hits and will meet Texas in the second game of the series today.
After Sanchez doubled in the first inning on the first World Series pitch he saw, he got things started for the Giants in the bottom of the third with San Francisco down, 2-0. Sanchez, who had previously doubled to opposite-field right, promptly doubled to left field to score Edgar Renteria to cut the deficit to 2-1.
"We were actually surprisingly calm in there," Sanchez said of playing from behind. "We still felt like we had a chance.
"We just tried to put the ball in play and we know [Lee] throws a lot of strikes."
The Giants would go on to tie the game at 2 before Sanchez helped spark a six-run fifth to give the Giants an 8-2 advantage. Sanchez gave the Giants a 3-2 lead when he doubled to center and then scored on a single by Cody Ross to make it 4-2.
Sanchez led off the sixth with a flyout to deep right before recording a run-scoring single in the eighth to extend San Francisco's lead to 10-4. He capped his night by scoring on a Nate Schierholtz single.
The Giants are looking to win the World Series for the first time since 1954, when they resided in New York, and Wednesday's outing would certainly seem to have them going in the right direction.
Said Sanchez: "I think this gives us a lot of confidence."
SF 11, Texas 7
4 for 5
Tonight at SF, 4:57 p.m.