The likes of Jeff Samardzija and Jason Hammel have provided optimism they would net a prosperous return in the likely event they're traded before the July 31 deadline, and Jake Arrieta has taken several steps toward showing he can provide quality at the top of the rotation if Samardzija and/or Hammel are dealt.
But the inconsistency of Edwin Jackson remains a lingering problem the Cubs may be forced to cope with.
Jackson's performance Wednesday night typified his mercurial style in a 4-1 loss to the Reds at unseasonably cold and foggy Wrigley Field.
After allowing a run in the first inning, Jackson allowed only one hit over the next four before a leadoff walk to Todd Frazier ignited a three-run sixth that resulted in his departure.
"Until we got to the sixth, he was in pretty good shape," Renteria said. "We were hoping he could eat up one more inning. It didn't work out.''
Cubs' starters, led by Arrieta (1.14), have a 3.55 ERA during the month of June. But Jackson's struggles inflate the statistic. His June ERA now has swelled to 6.23.
And getting off to a clean start has become a bigger challenge, as his ERA in the first two innings this season is 7.87.
With five weeks before the trade deadline, teams such as the Blue Jays, Red Sox and Angels continue to look at players in addition to Samardzija and Hammel.
The Blue Jays, who have sent nine scouts to watch the Cubs since last September, are believed to be looking for infield and relief help in addition to another starter.
But acquiring major league ready pitching may become a bigger necessity for the Cubs because of the struggles of Jackson (5-8).
"I've been feeling pretty good," Jackson said. "I know the results haven't been quite what I want them to be on a consistent basis.
"Aside from the start in San Diego (eight runs in four innings), I've been feeling pretty good. It's tough when you don't have the results according to how you feel."
The only sliver of optimism in Wednesday's loss was the continued resurgence of Starlin Castro, who had two hits and drove in the Cubs' lone run with a single off Mat Latos that tied the game in the fourth.
Castro's 45 RBIs through 76 games are one more than he had in all of 2013.
Latos, in his third start since returning from the disabled list, allowed five hits in seven innings.
"We faced some pretty good chuckers, too," Renteria said.