"We know we're not in it," Venable said. "But we come to the ballpark wanting to win, expecting to win. When you don't, it doesn't feel good."
Hermida had an RBI single in the first and a two-run single in the third as the Padres won for the first time since a 7-5 victory at San Francisco on Aug. 23. Venable tripled with the bases loaded in a four-run eighth inning.
Mat Latos (7-13) struck out eight in seven innings for San Diego, yielding two runs and five hits.
Colorado's Dexter Fowler had three hits, including a triple, for the second straight day. Fowler's 15th triple set a career high and franchise record.
The speedy center fielder now has seven extra-base hits in his last five games. He had two doubles and two triples in the three-game series at spacious Petco Park.
Jesus Guzman finished with three hits as San Diego avoided its first 10-game slide since last season. That losing streak in August and early September fueled the Padres' collapse after leading the NL West for most of the season.
Latos was determined to stop the skid.
"We've struggled a little bit here," he said. "I decided in my mind that I wanted to go out, and by any means necessary possible, and win this game."
The Rockies lost at San Diego for just the fourth time in their last 16 games. Colorado has won six of nine here this season.
"I felt like I was blind out there," said Colorado's Carlos Gonzalez, who struck out three times against Latos. "He was mixing his curveball and his slider was sharp, too."
Latos, who routinely throws his fastball in the mid-90s, said it was a conscious decision to use his off-speed pitches more.
"I feel like my curveball was really good," Latos said. "My slider was good later in the game. It kind of helped me out earlier on when it was looking pretty rough."
All of San Diego's run-scoring hits came with two outs.
"You feel good about yourself as a team when you get an early lead," Venable said.
Rockies starter Aaron Cook (3-9) only gave up four hits in six innings, but allowed three runs and walked four. The right-hander dropped to 14-6 with a 2.98 ERA in 28 career appearances against the Padres.
Hermida helped San Diego build a 3-0 lead with his two-out singles in the first and third.
"I think it was a matter of time before he got his hits," Padres manager Bud Black said. "He's too good of a hitter."
But the Rockies got two back in the fourth. Fowler led off with a triple and scored on Mark Ellis' grounder. Troy Tulowitzki drew a two-out walk and scored after consecutive singles by Jason Giambi and Seth Smith.
Colorado looked primed for an even bigger inning but Hermida ran down Kevin Kouzmanoff's drive into the right-field corner for the final out.
"Unbelievable," Latos said. "That was a big catch. It was definitely a game-changer."
The Padres recalled prized 1B prospect Anthony Rizzo from Triple-A Tucson. Rizzo hit only .143 with one homer and six RBIs in 35 games in his first stint with San Diego from June 9 to July 22. ... A sore right wrist kept Maybin out of the starting lineup for the eighth straight game. ... RHP Esmil Rogers will start for Colorado on Monday against Arizona LHP Wade Miley when the Rockies open a six-game homestand. ... Padres RHP Tim Stauffer attempts to rebound from his last start Tuesday at the Los Angeles Dodgers when he walked seven in 1 2/3 innings, including six in an eight-run second inning. Stauffer will face visiting San Francisco and LHP Madison Bumgarner on Monday.