Tejada knocked in two runs and finished with four hits -- his third consecutive multihit game in as many days -- to lead a 15-hit attack as San Diego opened its four-game set with the Cubs with a bang.
The Padres (70-47) got six shutout innings from pitcher Kevin Correia to move four games in front of the idle Giants in the National League West.
In addition to Tejada's four hits, Chase Headley reached base four times (two hits, two walks) and Chris Denorfia had three hits, the biggest being a two-run triple in the ninth inning to give the Padres a little breathing room over the Cubs (50-69).
But it was Tejada who proved to be the spark of the offense. After hitting just .189 in his first eight games following the trade, he's hitting .429 since (15-for-35).
What's happened with Tejada?
"Now I'm just getting good pitches to hit, not trying to hit them out. Now I just feel more comfortable," he said.
The same could be said for Correia (10-7), who joined Jon Garland, Clayton Richard and Mat Latos to reach double-digits in victories. Better still, Correia, who had a 5.26 ERA in the first half, is 5-1 with a 3.00 ERA in six starts since the All-Star break.
The key for Correia in this blissful stretch has been his ability to bury his fastball in the strike zone as well as getting a handle on three different breaking pitches that sometimes cooperate and sometimes don't.
"I was able to keep the ball on the ground for the most part," said Correia, who got eight ground-ball outs. "My fastball command wasn't as good as the year before, but now I feel like I've got that down."
The fastball wasn't down in the first inning, as the Cubs got hits from Kosuke Fukudome and Darwin Barney to start the game. But Correia got Marlon Byrd on a ground ball hit at Tejada and then struck out Aramis Ramirez on a curveball. After walking Xavier Nady, Correia got Alfonso Soriano on a fly ball to end the inning.
Correia cruised from there, though the bullpen had a few hiccups along the way. Luke Gregerson allowed two runs, Joe Thatcher allowed two inherited runners to score and Ernesto Frieri allowed three runs.
But Mike Adams and closer Heath Bell combined for the final four outs as the Padres improved to 3-1 on a 10-game road trip to San Francisco, Chicago and Milwaukee.
"They've got a nice ballclub," Cubs manager Lou Piniella said. "They added [Ryan] Ludwick and Tejada at the Trading Deadline, which gives them more pop in the lineup.
"They've got a good defensive club that has made only 50 errors all year and they've got a really nice bullpen to go along with reliable starting pitching. They've got the ingredients."
Tejada flew out in his first at-bat Monday against Cubs pitcher Tom Gorzelanny (6-7) before getting singles in the fourth and sixth innings. He had an RBI double in the seventh inning and an RBI single in the eighth inning.
"It was just a matter of time before he got consistent at the plate," said Padres hitting coach Randy Ready. "He uses the whole field, he knows how to move runners. He's a professional hitter."