"It's something I've been looking forward to," Castro said of facing the Astros. "Obviously, I played with a lot of those guys for a long time and still keep in contact with them. Being on the other side of the diamond is going to be fun. I know a lot of those guys so well that being on this side of it is going to be a new experience, but something I'm looking forward to."
Castro caught about half of Keuchel's starts during his 2015 American League Cy Young Award-winning season and broke McCullers into the Majors in 2015. Castro made his big league debut while the Astros were still a veteran-laden team in 2010, and was a steady presence behind the plate and in the clubhouse as the team was broken down and rebuilt.
"He was a big ingredient on our playoff team in 2015 and the work he did behind the plate and the development of some of our pitchers," Astros manager A.J. Hinch said. "How he posted every single day, I have a lot of respect for. It's going to be weird to see him in the other uniform for the first time and compete against him. He's got a little bit of insider knowledge on our team. Good guy, good player, someone who gave a lot of his time and energy to the Astros."
Castro said this year's Twins team, which leads the American League Central, is similar to the '15 Astros team that led the AL West for much of the year and wound up winning the AL Wild Card.
"What they kind of went through last year here and then coming back and having a lot of young guys kind of step up so far early, it's kind of reminiscent of '15 a little bit and what we were able to do then," he said. "It's been nice to be a part of it so far."
And Castro said seeing Keuchel recapture his Cy Young form and McCullers take a big step forward this year hasn't gone unnoticed.
"I haven't watched many of [McCullers'] outings yet, but we've talked and it's good to see him continually develop as a pitcher and learn a lot from some of the guys that are around them that pitch," he said. "Dallas does a really good job of that and him learning to do that will continually make him a better pitcher."
Brian McTaggart has covered the Astros since 2004, and for MLB.com since 2009. Follow @brianmctaggart on Twitter and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.