LOS ANGELES -- When Nolan Arenado and Charlie Blackmon hit back-to-back homers in the first inning on Friday night at Dodger Stadium, it seemed like it may be a good night for the Rockies. When Garrett Hampson added a third blast off Dodgers left-hander Clayton Kershaw in the fourth, Colorado appeared to be setting up well for its first victory at Los Angeles this season.

That was before things slipped away in a wild, long bottom of the fourth inning. In that frame, three Rockies pitchers combined to allow seven runs, which led to a 12-5 loss in the series opener against the Dodgers. The Rockies have lost their last 12 games at Dodger Stadium, dating back to June 30, 2018.

• Box score

Starter Peter Lambert's first pitch of the bottom of the fourth came at 9:39 p.m. MT. Wes Parson’s final pitch came 41 minutes later, at 10:20 p.m. MT. In between were five hits (including two home runs), three walks, a hit batter, two wild pitches, two stolen bases, an errant pickoff throw and an ejection of Dodgers manager Dave Roberts.

“With Peter, I think he got a little hurried,” Rockies manager Bud Black said. “You saw maybe a little bit of the inexperience show up tonight with Peter.”

The night started well for Lambert, who saw an uptick in his fastball velocity early. His four-seamer topped out at 95.6 mph, well above his season average of 92.6. The fact that Lambert did not throw a side session after his previous start may have helped with that.

“I felt pretty fresh out there, so that could have something to do with it,” Lambert said.

However, it wore off. From the third inning on, Lambert didn’t get his fastball higher than 93.2 mph. The right-hander entered the fourth with a three-run lead that was quickly cut down to two on Corey Seager’s leadoff homer. The rookie couldn't record an out in the inning, getting lifted three batters later with another run in and his pitch count up to 82.

“From my vantage point, it just looked like he got a little rushed, tried to do a little bit too much, and when you do that, there’s a tendency for your velocity to drop by trying to throw too hard and it sort of works against you,” Black said. “He lost a little bit of command and just couldn’t seem to pull it together.”

Sam Howard allowed the two runners he inherited from Lambert to score before Parsons came in to get the elusive final two outs. By then, 12 Dodgers batters had come to the plate, and the Rockies were down by four, a hole they couldn't climb out of.

Through 19 starts this season, Lambert has a 7.25 ERA, with likely only one outing remaining. Black opted to focus on how the Rockies and Lambert can take frustrating games like Friday’s to make him a better pitcher going forward.

“It’s a great learning experience for him to go through this season, right?” Black said. “Because he’s learned a great deal about big league pitching, and himself.”