Coincidentally, all three pitchers rose to the occasion with strong outings Sunday -- the day the Reds sent DeSclafani back to Cincinnati to have his elbow examined.
"I found it so refreshing on a day where we got bad news to start the day with Disco, to have two of our young, mostly Double-A starters come in and pitch so well on the same day," Reds manager Bryan Price said. "I thought that was a good omen for what we're facing here with only two spots in the rotation cemented at this point."
Romano, 23, has a 1.69 ERA through four games and 10 2/3 innings, with three walks and 16 strikeouts. The right-hander struck out seven over 3 2/3 innings in relief against the Brewers, including six batters in a row. He finished 2016 strong for Double-A Pensacola, going 5-1 with a 1.93 ERA while opponents batted .198 over his final 11 starts.
"I think I've earned the respect to be talked about for it, possibly," Romano said. "But it's not my decision. My job is to pitch, and the front office and coaching staff, it's their final decision. I feel like I can really help out the team in some possible way. I'll be ready for what they want me to do."
Davis, 23, started a split-squad game vs. the Rockies with Price watching on Sunday, and gave up two earned runs with two hits and three strikeouts over three innings. He has a 3.86 ERA over his three appearances.
"It was the best I've ever seen him throw," Price said. "Bottom of the zone, downward plane and velocity was back up to where it was before last year when he was injured."
Davis twisted his right ankle running out a double in the game, which affected him during his final inning of work. He is expected to OK, however.
"I felt like I put myself in a good position here, made some good pitches. Ultimately, it's not up to me," Davis said. "I felt my stuff played really, really well, especially against the lineups that I have faced. It's just being comfortable out there competing and making pitches."
Castillo, 24, was the most coveted prospect among the three the Reds acquired from the Marlins in January's trade for Dan Straily. He has a 3.60 ERA in three games, including two scoreless innings Sunday vs. Colorado.
The club wanted Castillo to develop consistency with his breaking ball, which he did effectively Sunday.
"I think I'm ready to be in the big leagues, I think my stuff is really good," Castillo said through translator Julio Morillo. "Being in big league camp when you're facing big league hitters, and you get them out, you have confidence in yourself and say, 'All right, my stuff is really good.' I think I'm going to be real close to making the team."
"I think two more weeks of evaluation and trying to define if any of them are physically capable of doing the job," Price said.
Mark Sheldon has covered the Reds for MLB.com since 2006, and previously covered the Twins from 2001-05. Follow him on Twitter @m_sheldon and Facebook and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.