CHICAGO -- There have been multiple points this season when various arms were either injured or unavailable out of the Cubs' bullpen. In those moments, manager David Ross realized how quickly an area of strength can be weakened.

"It's kind of hit me over the head," Ross said prior to Saturday's 6-0 loss to the Cardinals at Wrigley Field, "like, how fast your guys can get thin."

• Box score

With the struggling Cubs shifting into sell mode ahead of the July 30 Trade Deadline, Ross could be faced with a thin relief corps down the stretch this season. Closer Craig Kimbrel, in particular, will be an attractive commodity for October-bound ballclubs.

The list does not end there, though. Besides Kimbrel, Chicago's two primary setup men -- lefty Andrew Chafin (mutual option for 2022) and Ryan Tepera (free agent next winter) -- could also be on other teams' wish lists in the coming weeks.

Ross knows things would be challenging without his go-to trio.

"Sure," said the manager. "I definitely have felt that over the season already with guys that have gotten injured."

Saturday's loss, which was the 13th in 15 games for the Cubs, was another reality check, too. Continuing a season-long trend for Chicago's rotation, righty Zach Davies lasted only 4 1/3 innings. That is the 33rd time this year a Cubs starter has logged fewer than five frames.

Davies expressed frustration over his excessive pitch count (99 pitches) and not being able to give the Cubs "not necessarily the standard quality start, but just being able to get deeper in the game and get the bullpen a rest.”

Cubs catcher Willson Contreras took things a step further, speaking up about the team’s effort level as a whole. The high-energy catcher said the club seemed “distracted” by the upcoming All-Star break in a game that ended with Chicago being shut out for the eighth time this season, and the second time in the past three games.

“We have to win as a team,” Contreras said. “But also, I cannot ask everybody to play like I do, or to play like [Javier] Báez and I play. Everybody's different. I know they might be tired, but I'm here to win. I'm here to win. I'm here to compete. That's what I'd like to have from everybody else.”

While the Cubs' bullpen has been key for the club this season -- the group entered Saturday fourth in MLB with a 3.37 ERA -- the pile of short starts has put a strain on the staff. On Saturday, Davies' early exit contributed to a game-changing fifth inning.

Davies allowed a leadoff homer to Paul Goldschmidt in the fifth and was out of the game after facing two more batters. Lefty Adam Morgan then yielded a two-run homer to pinch-hitter Tommy Edman. Right-hander Dan Winkler later gave up a two-run shot to Paul DeJong. Keegan Thompson and Rex Brothers calmed the situation with two shutout innings apiece to close things out for Chicago.

But that five-run flurry did ample damage to push the Cubs (44-46) two games under the break-even mark once again. It was only a little more than two weeks ago that Chicago was atop the National League Central and exploring what pieces it could add for the stretch run.

Now, Kimbrel is searching for innings, having logged just two appearances in the past 14 games. His last save came on June 20. Still, the veteran All-Star has a 0.57 ERA with 54 strikeouts in 31 2/3 innings, making him a big trade chip for the Cubs.

Ross chuckled when asked about possibly being asked to manage the ninth without Kimbrel at his disposal.

"If we trade Craig Kimbrel, it's going to be hard to lock down wins," said Ross, who allowed himself to laugh a little at the obviousness of his comment. "I think everybody can agree with that statement."

Chafin, Tepera and Kimbrel have combined for a 1.83 ERA this season with 130 strikeouts and 32 walks in 108 innings. In the past two-plus weeks, their value to Chicago’s bullpen has diminished under the weight of an inconsistent rotation, laboring lineup and a heap of losses stacked one atop the other.

To Contreras’ point, the recent losing streak, the coming All-Star break and the sudden surplus of trade chatter has created a recipe for distraction.

“I think a professional team like this knows their job,” Davies said, “knows what they have to do and once we break out of that streak, take care of business. Hopefully it doesn't come to saying goodbyes to anybody. But it's baseball. We know it's a business, and you know that can change on a dime.”