"Obviously, we'd like to get back-to-back wins on the road," Renteria said. "Hopefully we can salvage this series tomorrow."
The Cubs launched three solo home runs in Saturday's contest, but the Phillies' bats fared better with men on base against Jackson.
Chase Utley got the scoring started in the bottom of the first with a solo blast over the scoreboard in right field. Mike Olt quickly got the run back for Chicago with a line-drive homer to left field in the top of the second.
But Jackson ran into trouble in the bottom half of the inning. After Marlon Byrd set the table with a leadoff triple, Domonic Brown, Carlos Ruiz and Reid Brignac all singled to put Philly up, 4-1.
Justin Ruggiano and Luis Valbuena followed Olt's example and hit solo home runs of their own in the third and fourth innings, respectively, to bring the Cubs within a run, but Jackson couldn't keep Chicago within striking distance.
The bottom of the fifth inning began with an exclamation point. Jimmy Rollins' single was the 2,235th hit of his career, an all-time Phillies record. There was a break in the action, as Mike Schmidt -- the previous record holder -- and the Phillies surrounded Rollins at first base with fireworks in the background.
Jackson threw some pitches while he waited, trying to stay sharp with all of Citizens Bank Park reveling in the history of the moment.
"It's part of the game," Jackson said, not making any excuses for anything that happened after the on-field delay.
Jackson proceeded to get Philly's two biggest bats -- Utley and Ryan Howard -- to fly out, but then he walked Byrd.
Jackson was a strike away from getting out of the jam, but he elevated a 2-2 fastball to Brown, who consequently sent it into the seats beyond the right-field fence for a three-run homer in what would prove to be the difference in the game.
"Pretty [poor] job of executing pitches, bearing down and making a pitch with two strikes and two outs with men on base," Jackson said. "It's what happens when you leave the ball over the plate. Especially when your team had battled back to get back in the game."
The Cubs tacked on a run in the top of the eighth, but could muster no more. Anthony Rizzo, Starlin Castro and Valbuena had consecutive singles with one out, but Nate Schierholtz grounded into an inning-ending double play with two men on base. Renteria challenged the out call at first, but it stood after replay review.
Jackson struggled to do what he does best -- eat innings. The right-hander, who has averaged 198 innings pitched per year in his last five full seasons dating to 2009, made it through just 4 2/3 frames against the Phillies, allowing seven runs (six earned) on eight hits and two walks while striking out two.
Jackson, whose ERA was under four on May 17, saw it hike to 5.11.
"The main thing has been just keeping the ball down," Jackson said. "Earlier in the year, I was keeping the ball down well. Now the ball is starting to come up and over the plate and hitters are getting good wood on it."
With the Trade Deadline looming in 2013, the Cubs made trades to cash in on two of their most valuable pieces, starting pitchers Scott Feldman and Matt Garza. They're approaching that point in the season again, when decisions have to be made about the direction of the team, especially with chips like Jason Hammel and Jeff Samardzija.
A series-capturing win on Sunday would be a good start in turning things around, but whether the Cubs could build off of taking two of three on the road would be the more critical factor in staving off what appears to be inevitable.
"Regardless of who is here, who isn't here, you take the field with the same approach," Jackson said. "You don't really worry about everything else."