CINCINNATI -- Prior to Monday night’s series opener against the Angels, Reds catcher Tucker Barnhart asked catching coach J.R. House if Luis Castillo pitched had against the club in Anaheim in June. When House said Castillo did not, Barnhart had a good feeling about the outing.

“When you haven’t seen his changeup, you can watch all the video you want, it doesn’t matter,” Barnhart said. “Until you get into the box, it’s a whole different ballgame. When you face a team for the first time, it makes it look even better than it is, which is difficult to do.”

• Box score

Castillo’s changeup is regarded as one of the best in baseball, and it lived up to that billing on Monday, helping him record a career-high 13 strikeouts over seven innings in a 7-4 victory at Great American Ball Park.

“I felt confident going out there,” Castillo said, via a translator. “I was prepared 100% for that game.”

Castillo finished the game with a career-high 119 pitches. He came back out for the seventh despite having 101 pitches through six innings, then he struck out three straight batters and walked off the field to a loud ovation.

“He was pushed, but he was strong and he wanted the ball,” said Reds acting manager Freddie Benavides. “He didn't want to come out of the game. For him to get into that elite group, you have to do that. He was the man tonight.”

Solo home runs by Luis Rengifo and Mike Trout accounted for the only runs off Castillo, who only allowed three hits and one walk.

The 13 strikeouts were the most against the Angels this season, surpassing Gerrit Cole’s 11 on July 17.

The Reds, who lead the Major Leagues with 93 first-inning runs, handed Castillo the early lead with five runs on five hits off right-hander Taylor Cole.

Nick Senzel’s bloop double to right field drove in two of the five runs.

The inning could have gone worse for Los Angeles after Trout dropped a routine fly ball, but a failed suicide squeeze bunt by Castillo helped end the rally.

"It's crazy,” Benavides said of the first-inning success. “But we have really good hitters at the top.”

Cole, who was scheduled to precede Patrick Sandoval on Monday, lasted only one inning.

The Reds scored their sixth run without a hit in the second when Jesse Winker walked, then advanced to third and scored on two wild pitches by Sandoval.

Rengifo’s home run to lead off the third was the first hit off Castillo.

In the sixth, Trout sent a 1-0 pitch from Castillo into the second deck of the bleachers in right-center for his 37th home run.

Trout’s homer came on a slider, Rengifo’s on a fastball. But it was Castillo’s signature changeup that the Angels couldn’t solve.

Castillo tied his season high with 26 swinging strikes -- which is the most for a Reds pitcher in the pitch-tracking era (since 2008). His changeup produced 18 of those swings.

Of Castillo’s 13 strikeouts, 11 came on changeups, the most any Major League pitcher has recorded on changeups in a single game in the past six seasons.

“That's my best pitch,” Castillo said. “When I feel good with that pitch, I can throw it in any count and any situation. It's a really important weapon that I have to get hitters out. I have to trust that pitch.”

It was the second straight strong outing for Castillo since allowing six runs in a 12-2 loss to the Rockies on July 26. On Monday, he regained his Cy Young Award-worthy form.

Castillo has allowed two earned runs or less in 17 of his 23 starts.

"Same thing we've been seeing from him all year,” Barnhart said. “There were a couple blips on the radar, but tonight was another wonderful start by him. He's a joy to catch. It's like playing a video game with him. A few times, I didn't even put a sign down. I knew what he wanted to throw and he threw it."