The bat didn't go as Zunino planned. He was hitting .221 after 28 games and had only two home runs. He was striking out more than usual and falling into bad habits at the plate.
That's when he went into O'Sullivan's office for a visit.
"From day one, he was our starting catcher," O'Sullivan said on Friday after the press conference. "I told him he was going to be in our starting lineup regardless. About a month later, we get to Omaha and he's probably our hottest hitter in the lineup and squaring up balls seemingly every at bat. It's a testimony to his mental toughness and ability to grind through things."
It wasn't easy for Zunino. He dislocated his left thumb after incorrectly catching a cutter from left-handed reliever Steven Rodriguez, and that came after breaking his right thumb early in the year.
The physical demands were one thing, but Zunino took pride in knowing the ins and outs of every Florida pitcher. That took time away from his hitting.
"It's something that I can always look back on and know how hard it was to go through them, and it makes struggles now feel easier," Mike Zunino said. "You learn when you're going through it. I've been at the bottom and seen what it's like at the top. It helps you enjoy every part of the game."
It's hard to enjoy anything more than what Zunino went through on Friday when he received the 26th annual Dick Howser Trophy, the baseball equivalent of the Heisman Trophy. He is the first Florida player to ever receive the recognition.
Zunino joins a group that includes plenty of well-known players, including Jason Varitek (Georgia Tech), Todd Helton (Tennessee), Jered Weaver (Long Beach State), Robin Ventura (Oklahoma State), Mark Teixeira (Georgia Tech), David Price (Vanderbilt), J.D. Drew (Florida State), Stephen Strasburg (San Diego State) and Buster Posey (Florida State).
It's an honor that never seemed possible as he rode through what felt like a season-long slump as a freshman.
"Not in my wildest dreams," Zunino said about imagining a career like this." I came here and we were hoping to get to the College World Series once and maybe win the SEC. Everything has blown my expectations right out of the water."
Zunino bounced back with a sophomore season that will go down with some of the best in Florida history. The catcher hit .371 with 19 home runs, 75 runs scored and 67 RBI. His team-high .674 slugging percentage was .129 higher than any other player.
That strong season led Florida back to Omaha, where Zunino had a conversation in the halls of the stadium with Jana Howser, the daughter of Dick. She congratulated him on the great season and leading his team to Omaha, but at the end of it, she told him she hoped she would be having a different conversation before the 2012 College World Series started.
Earlier this week, she did. Howser congratulated Zunino on winning the award over LSU left fielder Raph Rhymes and Utah Valley first baseman Goose Kallunki. This season, Zunino is hitting .322 with 19 home runs and 64 RBI.
"It means everything to all of us," O'Sullivan said. "It's such a great honor, not just for him and his family, but this program and our university to be the first at anything. To be the first winner of an award like the Dick Howser is a wonderful achievement for all of us. We all share in Mike's enjoyment of this award."
There aren't many weeks that go by without a new story about Zunino. Whether it's an important hit on the field or something he does off the field to inspire his team or others, it's what has made the Florida catcher special during his career. The Dick Howser committee was also clear that besides success on the field, they consider "leadership, moral character and courage" as attributes the winner must show.
Zunino has been that. The emotional leader of the Gators has been around the game as his dad, Greg, is a scout for the Cincinnati Reds. Those helped the intangibles that Zunino possesses.
"It means a tremendous amount," O'Sullivan said about Zunino's dad helping him understand the game. "He came in with a mindset and toolset that you knew he was going to be successful. He was much more advanced than most kids his age, especially playing such a demanding position as catcher.
"He understands the game of baseball to where he can separate his offense from defense. He never takes a bad at-bat out there and has a bad inning because of it. He can separate it."
When the Seattle Mariners took Zunino third overall in the 2012 MLB Draft, O'Sullivan picked up the phone to congratulate him. He expected it to go straight to voicemail, where he would congratulate him and thank him for what the junior has done for the Florida program.
With so many people calling, including the Mariners, O'Sullivan didn't expect to hear back anytime soon. Fifteen seconds after the left the message and hung up, Zunino was calling O'Sullivan back. He put off the his friends, family and Mariners representatives that were calling him to thank the head coach that got him to that point.
"That just sums up the type of kid he is," said O'Sullivan, shaking his head. "He gets it."