The light-hitting Padres broke out for a season-best nine runs in the sixth inning in a 13-3 rout of the Cubs on Thursday night. It followed a 14-hit performance in an 8-3 victory over the Cubs on Wednesday.
San Diego starter Tyson Ross (9-10) struck out a career-high 11, allowed one run, five hits and one walk in six innings. He reach a career high in wins after going 3-2 in five July starts, giving up just four earned runs in 35 innings.
San Diego led 3-1 entering the sixth. After the first two Padres reached base, Jackson (5-11) was pulled because of cramping in his right hand and was replaced by Brian Schlitter.
''I felt pretty good and then all of a sudden you go and you can't throw a fastball for a strike with my finger cramping,'' Jackson said.
Then the roof caved in on the Cubs, who were victims of San Diego's previous season-best offensive output on May 23 when the Padres beat them and Jackson 11-1.
Rene Rivera had three hits, including a home run, and drove in three runs. Will Venable had three hits and two RBIs, and Alexi Amarista and Chris Nelson also drove in two runs apiece with singles in the sixth-inning outburst.
The first nine Padres reached base in the sixth as San Diego, which carried an major league-worst .215 batting average into the game, sent 15 men to the plate.
''I thought we tried everything we could to minimize the damage, but it ended up kind of escalating,'' Cubs manager Rick Renteria said. ''It seemed like no matter who we used today it kept getting away. It kind of steamrolled.''
Jackson dropped his fourth straight decision over six starts, allowing five runs and seven hits. He hasn't won since June 20 against Pittsburgh.
He was followed by five relievers as Chicago lost for the 13th time in 16 games.
''We started the season struggling at the plate and now we've been hitting better,'' Rivera said. ''We're scoring more runs since the first half of the season. I think it was time to do it.''
The Padres tagged Jackson with two quick runs with two outs in the first.
The Cubs cut it to 2-1 in the fourth and had runners on second and third with two outs but Ross fanned John Baker to end the threat.
Rivera's solo shot to lead off the fifth made it 3-1.
National League home run leader Anthony Rizzo swung and missed a 3-2 pitch in the dirt with two outs in the fifth to apparently end the inning. But the pitch got away from Rivera, and Rizzo reached first with Arismendy Alcantara taking third.
Padres manager Bud Black asked for a review, claiming the batted ball struck Rizzo, but the play was upheld.
NOTES: The Padres plan to recall RHP Jesse Hahn and start him in Atlanta on Friday against LHP Alex Wood (7-7). Hahn, 24, is 5-2 in seven starts with San Diego this season. ... Padres rookie Jake Goebbert, a former Northwestern University standout, started in left field after sitting out Wednesday. Goebbert's parents own a pumpkin farm in nearby Hampshire, Illinois, and he had a large group of friends and relatives in the stands. ... Cubs C Welington Castillo was rested after drawing boos during Wednesday's 8-3 loss when he didn't run out a comebacker to the pitcher. ... Cubs LHP Travis Wood (7-9,) will face St. Louis' RHP Joe Kelly (2-1) on Friday.