CINCINNATI -- Luis Castillo wasn't just pitching well on Thursday -- the Reds starting pitcher was on a legitimate roll against Milwaukee's lineup. But as good as Castillo was, he was still on the losing side of a 7-2 defeat to the Brewers.

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The overriding question from the loss was: Did Castillo have one more batter left in him?

Over 5 2/3 innings, Castillo allowed only one hit and struck out seven with three walks, but was charged with three earned runs. The performance came on the heels of his six-inning, one-run start in a victory last Friday at St. Louis, which snapped a personal seven-game losing streak.

"I'm glad that these two outings have been working well for me," Castillo said via translator Jorge Merlos. "I've just got to keep working at it. You can't stop now, you have to keep going and keep trying to get better each time you go out there."

Castillo had overcome a shaky one-run top of the first inning and stayed loose during a 37-minute rain delay before the top of the fifth inning. The right-hander retired 15 in a row, with only two balls leaving the infield during that stretch.

"When you're throwing all of your pitches low in the zone, you're more than likely to get a lot of groundouts and strikeouts as well," Castillo said. "Those were working really well."

Jesse Winker's RBI single to left field gave Cincinnati a 2-1 lead in the bottom of the fifth.

In the sixth inning, after he struck out Luis Urías, Castillo issued back-to-back walks to Daniel Vogelbach and Christian Yelich. Against Avisaíl García, Castillo won the duel during a 10-pitch sequence that ended with a hard-fought strikeout.

"I know it’s easy to look at his ERA and his numbers and say he’s having a bad year. But the guy’s got elite stuff," Vogelbach said. "He’s got an elite changeup and he’s got 98 in the tank when he wants it. He was throwing strikes today and he made it tough on us, but we were able to have some long at-bats. Avi’s at-bat was unbelievable. It was one of those at-bats when you feel like something good is going to happen."

The GABP crowd roared as Castillo pumped his fist over retiring García.

"I was trying to make my best pitches there," said Castillo, who is 2-9 with a 6.47 ERA in 13 starts. "The changeup came really well, and that's how we got him to strike out that at-bat. I really knew that I had to focus really well in that at-bat and get him out. I didn't feel bad afterwards."

At that point, Castillo had thrown 96 pitches, and manager David Bell hoped Lucas Sims could pick up the third out from there.

"[Castillo] was still throwing the ball well. During the 10-pitch at-bat is when I made the decision," Bell said. "I felt like with the delay, he had to work extra hard to get that strikeout after the couple of walks. That’s why we had Lucas ready, and that was the thought process there."

However, on Sims’ fourth pitch, Milwaukee pounced, as Willy Adames hit an RBI ground-rule double over Tyler Naquin's head in center field. Jace Peterson followed with a two-run single that dropped in front of Winker in left field to give Milwaukee a 4-2 lead.

"Of course I'd like to have continued on. Those are not my decisions," Castillo said. "That's the decision of the manager. It's out of my control, so I have to respect any decision that he does make."

Sims has often been reliable for the Reds and came in having not allowed a run in his previous six appearances while pitching in seven consecutive wins. On the other hand, those mid-inning, big rally situations often belong to Tejay Antone first. 

"Tejay was not an option today. Lucas has done that for us and will do it a lot moving forward," Bell said.

Bell declined to elaborate on Antone. 

"If we could, I’d prefer to wait and talk about Tejay [Friday]," Bell said.

The Reds do need a starter on Sunday vs. the Rockies to replace the injured Sonny Gray. Antone hasn't been in a game since Sunday, but warmed up on Wednesday night.

Outside of Sims and Antone, the Reds' bullpen in general has been unreliable, and it showed again on Thursday. Sean Doolittle gave up Vogelbach's two-run homer in the top of the seventh inning, and Art Warren gave up back-to-back one-out doubles for another run in the eighth.

Cincinnati's bullpen ranks last in the Majors with a 5.88 ERA and leads the league with 39 homers allowed.

"I know it’s easy to talk about them as an entire group, but each individual pitcher is his own guy and has his own things that he’s working on, and we’ll continue to do that and continue to support them," Bell said. "I really believe things will get going in the right direction for our bullpen.”

Until then, it was a costly defeat as Cincinnati (29-31) dropped the rubber game of a three-game series and missed a chance to get back to a .500 record for the first time since May 16.