CHICAGO -- In his pregame discussion with reporters on Friday, Cubs manager David Ross was asked about the way the White Sox have pummeled left-handed pitching this season. Specifically, Ross was asked if veteran Jon Lester was aware of the South Siders' gaudy numbers off southpaws.

"I don't know if Jon's aware of it, but yeah, it's on my radar, for sure," Ross said. "Jonny's got his work cut out for him."

Those words proved prescient, as Lester allowed four of the White Sox’s six home runs in a 10-1 loss at Wrigley Field in the opener of a three-game set with the crosstown rivals. The game revealed a potential Trade Deadline need for the Cubs and was a study in contrast for the teams, which have picked up a pile of wins early on this season in different ways.

• Box score

On display Friday night was the dramatic difference in the teams' performance this season against left-handers.

The White Sox have throttled lefties on their way up the American League Central standings, and kept that trend going against Lester. The Cubs have won in spite of a subpar showing in that same category, and that continued with an anemic showing against Friday's starter, Dallas Keuchel.

Asked about the Cubs' offense before the game, during a session largely filled with talk about the Aug. 31 Trade Deadline, president of baseball operations Theo Epstein mentioned facing lefties as an area of deficiency at the moment.

"There's certainly things we're doing well," Epstein said. "We're seeing a ton of pitches and all that. We haven't really hit left-handed pitching that consistently yet. And we've gone through some of our contact issues and whatnot. Overall, I'd characterize our offense as doing enough to win, by definition.

"And also, not yet clicking on all cylinders. So I think there's a lot of room for improvement."

Heading into Friday night, the White Sox led the Majors with a .947 OPS against left-handers. They had a .576 slugging percentage off lefties, compared to a .362 showing by the Cubs, who had a .709 OPS off southpaws. The North Siders were 2 percent below league average (98 wRC+), while the South Siders were 55 percent above the MLB mean (155 wRC+) as a team.

Luis Robert (two-run homer in the second), José Abreu (three-run shot in the third), Danny Mendick (solo blast in the fourth) and Yasmani Grandal (two-run homer in the fourth) each cleared the wall on Friday against Lester. The veteran lefty lasted only 3 2/3 innings, in which he was charged with eight runs. The only other game Lester yielded four homers came on July 22, 2012, when he was with Boston, against Toronto.

“They have, obviously, some damaging power,” Lester said. “They're confident against lefties. They're swinging the bat well against them. And if you're not executing, if you're in there for 100 pitches and you're not executing 99 of them, they're going to make you pay.

“It's an impressive lineup. You just hope that the other guy doesn't pitch as well as Keuchel did tonight. Hopefully, you can outpitch the other guy. That's kind of what you're hoping right now with their lineup.”

Eloy Jiménez added a solo blast off Colin Rea in the seventh, and Abreu went deep for a second time in the ninth off Jason Adam, giving the White Sox six homers on the night. That established a single-game record in the history of the rivalry with the Cubs.

Against Keuchel, the Cubs went 1-for-16 in the first five innings and then had the makings of a rally with the bases loaded and no outs in the sixth. Nico Hoerner then popped out, and Javier Báez grounded into a double play to strand all three runners. Hoerner later ended Keuchel’s bid at a shutout with an RBI single in the eighth, but the Cubs stranded the bases loaded again.

Complicating matters right now is the fact that Kris Bryant (left wrist) is out temporarily and Steven Souza Jr. (right hamstring) is on the injured list. Willson Contreras (.536 OPS vs. lefties), Jason Heyward (.400 OPS) and Anthony Rizzo (.505) have also struggled against left-handers.

• Bryant out of action; Epstein discusses Trade Deadline

A year ago at the July 31 Trade Deadline, the Cubs added an impact bat in Nick Castellanos. Given the current economic state of the game, and the plethora of unique factors at this year's Deadline, Epstein said adding a star player is probably unrealistic for the Cubs.

"It's certainly a complicated landscape this year," Epstein said. "There are a lot of years when we know we have an impactful move or two in us, and it's a question of finding it and executing on it. This year, the moves might be more complementary, and there might be some internal solutions.

"In the game overall, you may still see those big moves -- like if there's a perfect match where one team's needs long-term complement another team's short-term needs, and you see a big trade. But there's certainly obstacles to that industry-wide and in our situation.

"We're not limiting ourselves [and not] dreaming about big names. We're certainly open to it, if it were to happen. We've done pretty big trades at the Deadline most years. But the smaller moves where you get incrementally better in a couple different areas, especially that address certain needs, can make a big difference as well."

The Cubs have their work cut out for them.