Andrew Cashner (8-7) gave up three runs on six hits in seven innings. He struck out seven and walked none.
De La Rosa was laboring to hold a one-run lead in the sixth after giving up a leadoff single to Jedd Gyorko, throwing a wild pitch and surrendering a single to Jesus Guzman, putting runners at first and third with none out.
Logan Forsythe hit a grounder to third and Gyorko broke for home. Third baseman Nolan Arenado threw the ball home to Torrealba, who chased Gyorko back toward third. As the two neared the bag, Torrealba managed to tag Gyorko on his back.
Torrealba then spotted Guzman barreling for third, made a dive in front of the sliding runner and tagged him out an instant before he reached the base.
"I guess it was the play of the game but it was just reaction," said Torrealba, who made the spot start in place of regular catcher Wilin Rosario (hamstring). "I really don't even know how I did it, to be honest with you."
Gyorko knows all too well how it happened.
"I got in a rundown and Torrealba made a pretty good play to get both of us," Gyorko said. "He ran that to perfection. I tried to stay in the rundown a little longer to give guys a chance to move up. That's the right play, it just didn't work out."
Rockies manager Walt Weiss said Torrealba's heady play exemplifies the way he plays the game.
"He gets pitchers through tough innings," Weiss said. "He brings a lot of positive energy every day. He's one of those guys who doesn't have to light up the box score to help his team win."
De La Rosa completed the escape from the inning by getting Ronny Cedeno to ground out.
Colorado added an insurance run in the eighth on Dickerson's RBI double.
The Rockies went up 3-1 with a pair of runs in the third. Dexter Fowler led the inning off with a single and one later, Dickerson tripled off the wall in the center. Tulowitzki followed with a single for his second RBI of the game.
San Diego closed to within a run in the fourth when Gyorko doubled with two outs and Guzman followed with an RBI single.
Colorado went in front 1-0 in the first on consecutive two-out doubles by Dickerson and Tulowitzki. Forsythe had a bead on Tulowitzki's deep drive to left field but the ball was knocked loose from his glove when he crashed against the wall.
The Padres evened the score on Chris Denorfia's RBI single in the third.
San Diego's Will Venable beat out an infield single in the fifth to extend his hitting streak to 11 games, a career high. ... The Padres return to San Diego to begin a 10-game homestand, their longest of the season. RHP Tyson Ross (3-5) is set to pitch the opener Thursday of a four-game set against RHP Zack Wheeler and the New York Mets. ... The Rockies head to Baltimore, where they'll open a 10-game road trip on Friday with RHP Juan Nicasio (6-6) going for Colorado against Orioles LHP Wei-Yin Chen. ... Rockies C Wilin Rosario was out of the lineup a day after tweaking a hamstring.
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DENVER, CO - AUGUST 14: Starting pitcher Andrew Cashner #34 of the San Diego Padres delivers to home plate during...