Ross issued a first-inning leadoff walk to Charlie Blackmon, but Padres catcher Christian Bethancourt -- competing for the job backing up regular catcher Derek Norris -- caught Blackmon stealing. The Rockies' Nolan Arenado singled to open the second, but Ross worked Gerardo Parra into a double-play grounder.
Rockies starter Tyler Chatwood, pitching against Major Leaguers for the first time since April. 29, 2014 -- his last start before Tommy John surgery -- gave up one run on one hit and two walks in two innings. Chatwood struck out two.
In the Padres' fifth, the big hits off Diaz were Jon Jay's RBI double and Alexei Ramirez's RBI single. Diaz, competing for a bullpen spot, was relieved by Gonzalez Germen, who fanned Brett Wallace to end the inning.
Bethancourt was hit on the hand by a Jason Motte pitch and left the game, but the Padres said the injury was not serious.
ROCKIES UP NEXT: Righty Christian Bergman, a key long reliever last season with the Rockies, will start against the Reds at Goodyear Ballpark ar 12:05 p.m. PT on Sunday. The Rockies will unveil two top starting ptiching prospects, righty Jeff Hoffman, who came in the Troy Tulowitzki deal with the Blue Jays, and lefty Kyle Freeland, the Rockies' top pick in 2014. Also, a pair of prospects -- righties Antonio Senzatela and German Marquez, will throw in a 10 a.m. B game on the D-backs' side of the Salt River Fields at Talking Stick complex.
PADRES UP NEXT: The Padres have a pair of split-squad games on Sunday, as one team will travel to face the White Sox at Camelback Ranch at 12:05 p.m. PT. Robbie Erlin makes his second appearance of the spring. He tossed one scoreless inning in the first game of spring against the Mariners. Erlin is hoping to win a job at the back end of the Padres rotation. James Shields will make his first start in the other game, as the Padres play host to the A's at 12:10 p.m. at the Peoria Sports Complex. Shields will be the No. 2 starter in the rotation behind Tyson Ross.
Thomas Harding is a reporter for MLB.com. Follow him on Twitter @harding_at_mlb, listen to podcasts and like his Facebook page. This story was not subject to the approval of Major League Baseball or its clubs.