LOS ANGELES — The Rockies came into Monday night’s series opener against the Dodgers in first place in the NL West by half a game and facing perhaps one of the most pivotal September road tests in franchise history. Consider part one of the test failed, and miserably so, as the Rockies flipped first place back to the Dodgers via Los Angeles’ statement 8-2 win. Adding insult to the loss in which Jon Gray imploded and the offense no-showed for the third time in four games was the fact that all-star shortstop Trevor Story exited due to an apparent right arm or wrist injury. Los Angeles began the blowout with Joc Pederson’s solo home run to lead off the first inning, and more traffic led to another run to make it a 2-0 Dodgers lead after one. And after setting down the Dodgers in order in the second inning, in the third Gray imploded in a fashion similar to the pressure-packed wild-card game in Arizona last season, when the right-hander was tagged for four runs in one-plus innings. Pederson stirred trouble again by leading off the frame with a double, Justin Turner followed with a single, and Manny Machado’s single scored Pederson.