"He's a big help behind the plate," Iwakuma said through translator Antony Suzuki. "You have a lot of confidence in him, and that gives you a lot of confidence to be able to bounce those split fingers and those sliders in front of the plate. That helps a lot to get these guys out."
Zunino, 22, works on that part of his craft constantly and is athletic enough to back up his work ethic with excellent footwork and good hands.
"We can't shy away from throwing his best pitch sometimes," Zunino said. "That's what we need. With the split, you aren't going to know exactly where it's going, but you just have to have trust in yourself and trust in him and center up the baseball when you block it."
Manager Eric Wedge, a former catcher, loves hearing about his pitchers' faith in the youngster.
"It's huge," Wedge said. "It's more of a team thing than anything because you're talking about a difference maker in the game. Look at some of the situations [Iwakuma was in Saturday], second and third with nobody out or a runner at third with one out and having to get those strikeouts. You know he's going to go to his splitty to do that. So for him to have that type of confidence in a young catcher, that's a big deal."
Closer Tom Wilhelmsen is another who is learning to trust the youngster.
"It's very important," Wilhelmsen said. "You don't want to be afraid to throw anything. It just gives you more confidence and more authority to throw that curveball in the dirt."
Greg Johns is a reporter for MLB.com. Follow him on Twitter @GregJohnsMLB as well as his Mariners Musings blog. This story was not subject to the approval of Major League Baseball or its clubs.