Sitting alongside Cain in a postgame interview session, Posey elaborated on the jitters he felt.
"It's a different type of nervousness than the World Series or playoffs," he said. "You want so much to put the [signals for the] right pitch down. Ultimately, this is the guy making the pitches. What I tried to do was just be confident in everything I called and not deviate from what I would have done in a tie game."
Obviously, all of Cain's deliveries proved effective. But Posey favored Cain's fastball, noticing its liveliness immediately.
"To me, his fastball was really jumping tonight," Posey said. "It had extra life on it."
When Cain wanted to throw something different, Posey readily agreed. One example occurred in the seventh inning, which Cain ended by striking out Jed Lowrie with a 3-2 changeup.
"There was no hesitation," Posey said.
Cain reciprocated by expressing confidence in Posey.
"Me and Buster were on [the same] page all night," Cain said. That bolstered Cain's confidence and helped him sense almost immediately that a big game was in store.
"Probably the first time through the lineup I felt like something could happen," Cain said.
Considered one of the most underrated pitchers in the Majors, Cain will undoubtedly gain recognition and prominence as a result of his perfecto. Posey, of course, already knows all about Cain's skill.
"He's one of the best arms in the game," Posey said. "I'm lucky to be able to work with him every fifth day."
A year ago, Posey was recovering from multiple left leg injuries that he sustained in a home-plate collision with Scott Cousins of the Marlins. Now, the catcher is playing frequently and productively, leading the Giants in home runs and RBIs and pacing the National League All-Star balloting at his position. Besides working with Cain, Posey went 2-for-5 with a double and a run scored Wednesday.
"I couldn't be happier for Buster Posey," Giants manager Bruce Bochy said. "You can go your whole career and not catch a no-hitter, much less a perfect game. He deserves a lot of credit. He called a great game and they were in sync the whole time."
As a catcher, Houston's Chris Snyder fully understood Posey's contributions to Cain's historic effort.
"Cainer, Posey, both of them the way they worked tonight and at the end of the day it was perfect," Snyder said. "All the respect to both of those guys for the way they worked tonight. [Cain] made some tough pitches, he had some 3-2 counts and threw a couple of 3-2 breaking balls for punchouts. In that situation, it's tough to do. Hats off to both of them."