"They feel good working together; sometimes maybe that's a winning combination," interim manager Tony DeFrancesco said. "When you look around, there's some guys who catch knuckleballers better, there's some guys who catch veterans better, but we're just going to go out right now and try to get the best matchups that we can day in and day out."
Harrell struggled on Tuesday, surrendering six runs over five innings in his first time working with Castro since his fourth start of the year.
"Pitchers sometimes need a little bit of extra help, and whatever we can do to get Lucas on track, we'll do whatever we can," DeFrancesco said.
Catching for Harrell has given Snyder a consistent work schedule this season, which was not guaranteed when he signed this winter. Snyder was given a one-year deal (with a mutual option for 2013) in January -- one month after Castro underwent surgery to remove a bone in his left foot that ultimately forced him to miss part of Spring Training.
As a result, the two have formed a nice tandem behind the plate for the Astros, the veteran Snyder serving as a mentor to the 25-year old Castro.
"I think they're feeding off each other," DeFrancesco said. "Snyder does a great job leading. It seems like Castro's been around here a while, but his Major League playing time has been shortened by some of his injuries. But we're trying to get him back there, understanding our pitching staff and leading."