Sanchez sent everybody home with a two-run shot off Rex Brothers in the bottom of the ninth. The Giants now head home to play the Oakland A's in the three-game Bay Bridge Series. San Francisco finished the Arizona portion of its exhibition schedule with a 16-11-1 record.
Arenado continued a hot spring by driving in three runs. The Rockies opened the scoring with a pair of first-inning runs off Cain. Charlie Blackmon walked, advanced to second base on an infield out and came home on Troy Tulowitzki's double. Carlos Gonzalez also doubled, sending in Tulowitzki.
Corey Dickerson walked and scored on Arenado's third-inning triple, widening Colorado's lead to 3-0.
Arenado, batting .373 this spring after a 2-for-4 effort, doubled home Tulowitzki and Gonzalez with a fifth-inning fly ball that the wind carried off the center-field barrier. Arenado advanced to third on Ryan Wheeler's single and scored on a forceout.
That provided ample support for De La Rosa, who blanked San Francisco on three hits through six innings.
Cain lasted five innings, allowing six runs and nine hits. He finished with a Cactus League ERA of 7.47 in four starts.
Masset started the eighth inning for the Rockies and got two quick outs. Then Juan Perez singled and stole second, and Tyler Colvin walked. Then Belt struck out swinging, but it was on a wild pitch by Masset, and Belt reached first. That extra out was penal, as Parker cracked the next pitch for a grand slam, tying the score at 6.
Up next: The Rockies are off Thursday, although lefty Brett Anderson will pitch in a Minor League game. On Friday, righty Tyler Chatwood is set to start against the Mariners in Peoria, Ariz., with back-of-the-game arms Brothers and Hawkins scheduled to work.
Chris Haft is a reporter for MLB.com. Read his blog, Haft-Baked Ideas, and follow him on Twitter at @sfgiantsbeat. This story was not subject to the approval of Major League Baseball or its clubs.