CHICAGO -- Cubs manager Joe Maddon did not mince words earlier this week when discussing his offense's production against left-handed pitching this season.

"We've been terrible. We have to be better," Maddon said before the weekend series against the Padres. "If you look at the overarching, overall numbers, they're not good, and we have to be better at that."

Those comments came to mind on Sunday, when Chris McCosky the Detroit News reported that the Cubs are among the teams showing interest in Tigers outfielder Nicholas Castellanos ahead of the July 31 Trade Deadline. Chicago will be exploring a few trade avenues over the next 10 days, with potentially adding some offense (especially to help against left-handed pitching) on the to-do list.

According to the report, the talks between Chicago and Detroit have "some teeth."

Entering Sunday's game against San Diego, the Cubs ranked 13th in the National League in batting average (.243) and eighth in OPS (.778) against lefty pitching. They ranked seventh in weighted runs created plus (101) and wOBA (.328). Since June 1, David Bote (.615 OPS and 55 wRC+), Albert Almora Jr. (.499 OPS and 35 wRC+), Jason Heyward (.392 OPS, zero wRC+) and Kyle Schwarber (.389 OPS and minus-three wRC+) had all struggled against southpaws.

The 27-year-old Castellanos -- under contract for $9.95 million but a potential free agent after this season – entered Sunday batting .377 with a 1.090 OPS and 184 wRC+ in 71 plate appearances against left-handed pitching this year. Overall, the right fielder was batting .280 with 10 homers, 33 doubles, 35 RBIs and an .807 OPS with a 111 wRC+ through 92 games for Detroit.

Defensively, though, Castellanos has logged minus-seven defensive runs saved with a minus-6.5 UZR/150 in 726 1/3 innings in right field this year. Over his career, he has minus 33 DRS across 2,133 2/3 innings in right.

Acquiring a player like Castellanos would give Maddon some more flexibility with how he mixes and matches his outfielders based on platoon advantage. Schwarber plays left against righties but typically is on the bench against southpaws. Heyward can move between right and center. Kris Bryant has played both corners. On Saturday, switch-hitter Robel Garcia was tested in left field with a left-hander starting for San Diego.

"I'm still saying there's another level of us that I want to see," Maddon said. "We've got to hit lefties, man. We've got to figure that part of it out. That's a big part moving down the road. And we have guys in our lineup that historically have done that that aren't doing it right now."

Worth noting

• Bryant started in left field on Friday, in right field on Saturday and at third base on Sunday against the Padres. The slugger's willingness to move around the diamond has enabled Maddon to utilize an assortment of defensive alignments this year. Overall, Bryant has started games at third (58), right (19), left (10) and first base (three) this season.

"He's playing as good as he can play right now," Maddon said. "I really like what I'm watching -- we all do. It's huge that he's been able to do that, and he does it without complaint. It's so important to what we're doing right now. With him not being able to do that or being recalcitrant in any way would be really difficult to make this whole thing work."

• Left-hander Cole Hamels (10-day injured list, left oblique strain) got through his bullpen session Saturday without any issues, and the Cubs are now in the process of determining his next step. It is likely that Hamels will begin a Minor League rehab assignment in the coming week.

•  Catcher Willson Contreras (10-day IL, right foot strain) continues to progress well. Maddon did not rule out activating him when eligible Wednesday in San Francisco.