"From the small sample size, I can tell from seeing him a couple years ago to now, there's a big progression. It's day and night. You can tell he's been working hard.
"He's come a long way and he knows that himself, so having that confidence, as well, will help him."
Castillo, 26, batted .274 last season, his first full year in the big leagues, and hit a career-high eight home runs. He's doing everything he can to avoid a sophomore jinx.
"When you're a rookie, you need to get the respect of everybody," Castillo said. "You work hard, and they saw what I did, and that's how you get respect. I have to learn from my mistakes and keep working hard. I have to make them feel comfortable with me. They know what I'm doing behind the plate. They see me spending a lot of time in the video room. This year will be way easier than last year."
What will help this year is knowing the amount of advance work that pitching coach Chris Bosio and catching coach Mike Borzello demand.
"You've got to be prepared before you go into the game, and he's doing that," Bosio said. "Welly's doing great. He's worked hard, is real passionate about what he's doing and getting better. He's really coming into his own as a young guy. He's improved as much as any young catcher I've seen in my 32 years now. We're lucky to have him. He's intelligent and he's passionate. It's a good mix."
He's also still learning. Castillo got his first look at Reds' speedster Billy Hamilton on Saturday. Jason Hammel walked Hamilton, who stole second on a swinging strike three. Castillo didn't get a good grip on the ball. Hamilton then took off and swiped third, and Castillo's throw was a tad late. Hammel blamed himself for the steal of third.
Castillo did figure out a way to keep Hamilton off the bases in the second, when he made a nice, back-handed catch near the Reds' dugout of the center fielder's popup.
"[Castillo] gave me a good target," Hammel said. "He's a very positive guy back there. I like it. There were just a couple times when I shook [him off]. But in Spring Training, you get a lot of shakes if you're working on stuff. I think we're going to be good to go."
If Hammel needed an endorsement of the Cubs' young catcher, he could just ask Jeff Samardzija.
"The way he's improving is unbelievable," Samardzija said of Castillo. "We expect a lot of each other, and I really like where we're at with him behind the plate and me on the mound."
"The communication these guys have with him is good," Bosio said. "We're trying to match up 'Welly' with all our starters as best we can. It's important to be comfortable. It was a perfect situation [on Feb. 27] -- Jeff, like a lot of the guys, it was the first game, 14,000 home crowd, he's overthrowing, and boom, Jeff goes to his secondary stuff and ends up getting out with strikeouts. It's a sign of maturity on all ends."
It's been a quirky spring. Castillo was slowed because of some soreness in his legs from all the early work in camp. Then, he was accidentally hit in the face by a ball while hitting in the cages.
Castillo does need to be more consistent at the plate, not just behind it. He batted .312 in April, but followed that with a .230 May. In the first half of the season, he batted .266, and batted .288 in the second half. What was the difference?
"I felt like I just started to get more comfortable and knew the pitchers more," Castillo said of the second half. "I felt like, 'Hey, I belong here.' Facing the same guys, the same teams a couple times, I think I know how they're going to pitch me. I just simplified everything. Don't try to think, don't try to do too much.
"[I told myself], 'You've done this your whole life. This is your time.' That's what I had in my mind. That's why I had a better second half than the first one."
Which is why the Cubs expect a better season this year than last.