"It's unacceptable to pitch a game like that," Jansen said.
Everth Cabrera's sacrifice fly capped San Diego's three-run ninth.
"When I hit the flyball I celebrate like it was a walk-off bomb," Cabrera said. "Especially against the Dodgers with all their fans from LA here."
It was the Padres' third consecutive win and it snapped a three-game winning streak by the Dodgers.
Trailing 5-3, Alexi Amarista opened the San Diego ninth with a single off Jansen and scored on Carlos Quentin's pinch-hit double. Venable tied the game when his double scored pinch-runner Andrew Cashner. Venable took third on Rene Rivera's sacrifice and scored on Cabrera's deep fly to right.
"The last three days, we played real baseball," Cabrera said.
Dale Thayer (3-2) pitched the ninth for the victory.
Yasiel Puig, who had two RBI for the Dodgers, left in the eighth inning with a mild left hip muscle strain.
Seth Smith homered twice, doubled and walked for the Padres. It was Smith's sixth multi-homer game of his career.
"I came in early and worked on some things," Smith said. "It's fun when you put in the work and you see the results."
The Padres' bullpen, which has been strong all season, threw four scoreless innings to keep the game close.
"All year long those guys have done their thing," Black said.
After Smith's second homer in the sixth, the Padres had the tying runs aboard when Cameron Maybin reached on a fielder's choice and Amarista walked. But Jace Peterson struck out to end the threat.
The Dodgers scored three times in the fifth, aided by two wild pitches and an error by Amarista at third base.
With runners in scoring position and the infield playing up, Puig hit a one-out grounder between third and shortstop which deflected off the gloves of Amarista and Cabrera into short let field to score Dee Gordon.
Amarista retrieved the ball and when his throw home was wide, Hanley Ramirez scored on the error.
Puig advanced to third on the play and scored on Adrian Gonzalez's sacrifice fly for a 5-1 lead.
Gordon opened the game with a triple and scored on Peterson's errant relay throw to third. Later in the inning Gonzalez doubled and Matt Kemp drove him in with a base hit to left off Amarista's glove for a 2-0 lead.
Smith homered to right-center in the first to bring the Padres within 2-1.
"There are always close games with these guys," Dodgers manager Don Mattingly said. "To me, they are one of those clubs that are tough to beat."
The National Baseball Hall of Fame requested Clayton Kershaw's cleats from his Wednesday no-hitter. Kershaw said his accomplishment has started to sink in. "I couldn't sleep very well that night obviously, then the next day to turn on the TV and hear about it was pretty cool stuff." ... Dodgers OF Carl Crawford (left ankle sprain) is still unable to do baseball activities, Mattingly said. ... Padres 3B Chase Headley was out of the lineup with a sore back. ... Padres LHP Robbie Erlin (left elbow soreness) has increased his throwing program and could join the team on its upcoming trip. There is no date for his return. ... Dodgers RHP Josh Beckett (4-4, 2.49) faces Padres RHP Tyson Ross (6-6, 3:27) on Saturday night.