DENVER – Coming off three straight tight and impressive victories, San Diego took an embarrassing step backward, allowing seven runs in the first inning in their most lopsided loss of the season, 20-1 to the Colorado Rockies.

Matt Holliday hit two homers for Colorado. His eight RBIs were a career high, the most in the NL this season, and it tied the franchise record, as did Colorado’s 20 runs.

The loss dropped the first-place Padres to 75-75. That’s still five games ahead of San Francisco in the NL West, although after this game, the punch lines are sure to keep rolling in about the so-called “race” in that woefully weak division.

Who starred for Colorado?

Who didn’t?

Holliday homered onto the left-field concourse and off the left-field foul pole en route to his career night. Luis Gonzalez had four hits and four RBIs, also a career high. Relief pitcher Marcos Carvajal had his first major league hit, a two-run single in the seventh that made it 17-1 … the list went on and on for the last-place Rockies, who have won as many games as anyone in the NL West since June 1.

San Diego starter Woody Williams (8-12) was lifted before he could get an out in the second inning, having allowed nine runs and nine hits. Combined with the six runs he gave up in 3 1-3 innings on opening day at Coors Field, Williams’ ERA against Colorado this season shot up to 29.10.

By the time reliever Scott Cassidy got the Rockies out after the second, it was 10-0.

But there is no 10-run rule in the majors and, an inning later, Colorado had bumped it to 15-0. San Diego manager Bruce Bochy responded by emptying his bench to start the bottom of the fourth, subbing in players at every position except left field and first base.

The biggest suspense after that was whether Bochy would turn to a position player to pitch in hopes of conserving his bullpen for the stretch run. He did – bringing third baseman Sean Burroughs in to work the eighth. Throwing 75 mph “fastballs,” he allowed four hits and three runs, including Holliday’s foul-pole shot, in his first major league pitching appearance.

The beneficiary of Colorado’s big night was Jamey Wright (8-16), who was recently demoted to the bullpen but got a spot start because of an injury to Byung-Hyun Kim. Staked to the 7-0 lead, Wright prevented any Coors Field comeback in this one, holding the Padres to one run and five hits over six innings.

The Rockies tied a franchise record for runs in the first inning, sending 11 batters to the plate and hitting for the cycle. Dustan Mohr’s two-run homer was the highlight. It gave Colorado a 6-0 lead.

The 20 runs were the most San Diego has allowed this season. And while every team has awful nights like this, the timing was particularly bad for the Padres.

They had won three straight close, dramatic games – and four in five nights – and their 8-7 victory over Colorado in the series opener Monday put them over .500 after leading the division at or below the break-even point for more than a week.

As Tuesday showed, they aren’t quite at full stride yet.

Paired with San Francisco’s 4-3 win over Washington, the Padres’ magic number stayed stuck at eight.

Notes: This marked the fifth time Colorado has scored seven runs in the first. The last was July 11, 1999, against the Angels. … Williams had allowed only one earned run in each of his last four starts. … With the win, Wright avoided joining Darryl Kile with the franchise record for losses in a season (17).