A two-run homer by former Padre Yonder Alonso triggered a four-run, sixth-inning rally Sunday afternoon that led the visiting Colorado Rockies to an 8-3 victory over San Diego.German Marquez (11-5) helped the Rockies avoid a sweep in the four-game series by holding the Padres to three runs on five hits with nine strikeouts in eight innings. He exited after tossing 93 pitches, 68 for strikes.San Diego right-hander Dinelson Lamet allowed only one hit over five innings before Charlie Blackmon singled to open the sixth. Alonso followed with a 393-foot homer for his second game-tying homer in as many games and third since joining the Rockies.Craig Stammen (6-6) replaced Lamet and gave up two runs on four hits.Ryan McMahon greeted Stammen with a double and scored on Ian Desmond’s single.Stammen retired the next two batters before Marquez helped his own cause with a bloop RBI single to center field.The Padres built a 2-0 lead against Marquez on solo homers to right-center field by rookies Francisco Mejia and Josh Naylor in the second and third innings, respectively. It was the sixth home runs of the season for both.The Padres cut the lead to a single run in the bottom of the seventh. Hunter Renfroe drew a lead-off walk, moved to third on a Mejia single and scored on a double-play grounder by Greg Garcia.