CHICAGO -- It's a game almost every manager plays at some point in the regular season: Who do you trust in your bullpen? It's a game that has found its way to Chicago Cubs skipper Joe Maddon's office as he attempts to map out a strategy with his relievers that won't blow up in his face.

With a collective 5.76 ERA and 1.65 WHIP for his relief staff since the All-Star break, Maddon hasn't exactly been winning at that game lately. But whom can he trust? It doesn't look like it's righty Justin Grimm, at least right now. Grimm served up his ninth home run of the season Monday in just his 38th inning pitched.

"The stuff is good, just making mistakes with his fastball," Maddon said after the 3-1 loss to the White Sox. "If you look at those nine home runs, I would bet they're almost all on fastballs."

Eight of those nine home runs have been against Grimm's fastball, including Adam Engel's tie-breaking homer in the sixth inning Monday. Grimm says he is feeling really good, but until the results come, it's hard for Maddon to win the "Whom do you trust?" game with Grimm on the mound. His ERA is 5.40 after the loss.

"In the big picture of things, I think it's the long ball this year that makes [my ERA] look worse than it really is," Grimm said.

Chicago's Justin Grimm allowed his ninth home run of the season on Monday, a solo shot to Adam Engle that broke a 1-1 tie in the sixth. AP Photo/Charles Rex Arbogast

What about 42-year-old Koji Uehara? Can Maddon trust him? Uehara was the clear set-up man during the first half, but Maddon will use the right-hander only in certain situations, especially when a team is susceptible to high fastballs. But Uehara has given up a home run in two of his past four appearances -- including a solo shot to Matt Davidson on Monday -- after surrendering only one long ball in the first half.

"He knows he has to be sharper," Uehara said through his interpreter. "There's nothing especially wrong, just needs to be better."

Uehara has an 8.10 ERA in the 3 1/3 innings he has pitched since the second-half began, so cross him off for now as well.

Even closer Wade Davis is having his moments, despite a perfect record in save opportunities. He has a 4.50 ERA with four walks in four innings pitched since the break, but if Maddon can't trust a guy who is 2-0 and 20-for-20 in save chances, whom can he trust? Davis should -- and will -- get the ball every chance Maddon has to give it to him.

Perhaps Maddon can turn to an old face who has actually burned him in the past in the trust game. Righty Hector Rondon is all of a sudden hitting triple digits on the radar gun and looking like a former version of himself, one that dominated as a closer for the Cubs in portions of 2015 and 2016, though he had his trying moments in between.

"My mechanics are good," Rondon said before Monday's game. "I feel really good. Coming in the other day with the bases loaded [and giving up runs,] that pissed me off. So I came in [Sunday] and was more aggressive."

According to ESPN Stats & Info, Rondon's average fastball velocity before the break was 95.8 mph. It's up to 97.4 since then, and his off-speed pitches are looking better as well. He's a risk to trust, but Maddon needs someone to pitch those middle innings. Actually, the manager might need someone to pitch the later innings too, as Carl Edwards Jr. is another one who is being tested. He gets out of jams more often than not, but he continues to get into them as well. Six walks in four innings since the break begin to tell his story.

The two most trusted arms in the pen right now might be Brian Duensing and Pedro Strop. Strop moves back and forth from the "do not pitch" category, but Duensing has been as steady as anyone, as evidenced by his 2.57 ERA and just 10 walks in 42 innings pitched.

There's one conclusion Maddon can make from playing the trust game: He can trust the front office to help him out down the stretch. With less than a week left before the non-waiver trade deadline, Maddon's bosses need to give him a better chance to win the game and, subsequently, the division. Either a righty or lefty would work, but the bigger need seems to be coming from the right side -- someone Maddon can plug into innings 6 through 8 if need be.

Otherwise, perhaps Grimm can work his way back into the trust category. He says his stuff is good, but it needs to show up on the mound as the Cubs battle for a third consecutive playoff appearance.

"For the most part, that's probably the best I've felt, control-wise, since a couple years," Grimm said. "On the bright side, that's a positive note. There [are] things I've been working on the past couple of days to get on top of the baseball. Today I saw that really play out in a positive manner, for sure.

"If I do that over the next two months every time out, the results will take care of themselves. I thought I was really dominant today, other than one pitch."

Can Maddon trust him?