WASHINGTON -- When watching Luis Castillo throw with Double-A Pensacola this season, Reds manager Bryan Price has been impressed with the right-hander's ability to mix his changeup and fastball. Price said Castillo doesn't need to rely on his fastball for strikes the way some pitchers do since he can throw his changeup for strikes just as effectively.
That skill was one of the reasons the Reds called up Castillo to make his Major League debut against the Nationals on Friday night. The Reds made room for Castillo by sending Amir Garrett to Triple-A Louisville.
"The most important [thing] is [for Castillo] to throw his game; do what he's doing in Double-A that's been effective," Price said. "That's being able to mix the two pitches, create a tough situation for the hitters to stay on-balance between the fastball and the changeup, use the slider at the right times and do the things that he needs to do to give us a chance to win a ballgame."
Castillo is the fifth-best prospect in the Reds' organization according to MLBPipeline, and has played in the Minor Leagues since 2012. In 14 starts with Double-A Pensacola this year, the 24-year-old holds a 2.58 ERA and has walked just 13 of the 317 batters he's faced.
Garrett made his Major League debut earlier this season, but he has a 7.41 ERA in 12 starts. He allowed six or more runs in five of those outings.

In his last start Tuesday, Garrett surrendered six runs in 3 2/3 innings in a loss to the Rays. Garrett went on the disabled list for 11 days on May 25 with a hip injury, and left his June 9 start in the second inning when he suffered a left hand contusion from a line drive that struck his hand. The right-hander said those injuries played a role in him losing his rhythm.
"You have to trust the process," Garrett said. "I'm just going to go [to Louisville] and do my thing, find my swagger, just get it back. Dominate back down there a little bit and come back up here ready to ball. It's a reality check for me."
Garrett was scheduled to start against the Cardinals on Monday, and Price said Brandon Finnegan, who's been on the DL since April 16 with a shoulder injury, is in the mix to start. Finnegan has made three starts in the Minor Leagues this month and pitched to a 3.00 ERA. Though he allowed four runs in five innings with Triple-A Louisville on Wednesday, Price said it was promising that Finnegan felt well. Price isn't sure whether Finnegan will make another Minor League start.
Finnegan has a career 3.76 ERA and held a 2.70 ERA in three starts with the Reds to begin this season. He could help a pitching staff that entered Friday with the second-worst ERA in the Major Leagues (5.08).