Billo took a perfect game into the sixth inning as Class A Kane County blanked Peoria, 6-0.
The Royals' 28th-round pick in 2008 retired the first 17 batters of the game before allowing a single to Ben Klafczynski with two outs in the sixth. Billo recovered to get Taiwan Easterling to fly out to center field, ending his night.
"I had him 0-2 and I was trying to throw a fastball away. I just left it up and he hit it up the middle," Bill said. 'I did realize [the perfect-game bid]. I've taken it to 5 2/3 innings before and I was hoping to take it six."
Billo finished with three strikeouts and retired 10 batters on groundouts.
"My fastball location was pretty good," he said. "I was able to keep the ball down and I was able to change speeds with my change-up and curve to keep them off balance."
Billo (9-2) lowered his ERA to a Midwest League-leading 1.40 and is ranked second with a 0.95 WHIP. The 21-year-old right-hander has appeared in 23 games -- including 14 starts -- and has struck out 105 batters over 115 1/3 innings for the Cougars.
"I would hope so," Billo said about staying in the rotation. "I like coming out and starting the game. I don't mind relieving if that's what the Royals have planned for me, but I'd like to be in the rotation."
While the idea of a promotion has crossed his mind, Billo thinks his place is in Kane County for the rest of the season.
"I think I'll probably be here the rest of the year," he said. "We are in playoff contention and we'd like to make the playoffs."
Cheslor Cuthbert, the Royals' No. 10 prospect, doubled twice and drove in three runs while Brian Fletcher was 3-for-4 with two runs.
Austin Kirk (5-8) took the loss for the Chiefs, allowing five runs on 10 hits over 4 2/3 innings.