"I haven't seen it yet," Descalso said, "but I know what I did."
What Descalso did was end a troubling bottom of the fourth inning that began with St. Louis in control, 6-0, but saw San Francisco mount a comeback. The lead was down to two, and Cardinals starter Lance Lynn was out of the game when Giants outfielder Angel Pagan stepped to the plate with two outs and two runners on base.
Pagan beat reliever Joe Kelly's first-pitch fastball into the ground and sent it up the middle, where Descalso ranged to his right for a diving stop, before flipping the ball to shortstop Pete Kozma for the inning-ending out.
"I knew he didn't hit it that hard," Kelly said, "and that our middle infielders are playing well, and that Descalso is one of the best we have out there. I knew he hit it soft enough that we would have a chance at it. It was a good play. If [Pagan] had hit it harder, it would have been a base hit."
Descalso did not know then that it would be the final threat for either team.
"It's only the fourth inning, you don't know what's going to happen over the next five innings," he said. "It turns out, shutting that down with only giving up four [runs] was a pretty big turning point."
Another came in the fifth inning, when Cards first baseman Allen Craig made a diving stop to rob Pablo Sandoval of a hit down the line. Had the baseball made it through, the Giants would have had at least runners at first and third with nobody out. Instead, Kelly and left-hander Mark Rzepczynski navigated through a scoreless inning.
"They've got a very potent offense, and they're good on both sides of the ball," San Francisco first baseman Brandon Belt said. "They're going to be a tough team to beat, and we're going to have to be on our 'A' game for sure."
Adam McCalvy is a reporter for MLB.com. Read his blog, Brew Beat, and follow him on Twitter at @AdamMcCalvy. This story was not subject to the approval of Major League Baseball or its clubs.