"At first, I thought maybe it was a pitching journal," said Carlin, who is now a catcher with the Indians. "'I was like, 'Hey, good for him. He's keeping track of the hitters. That's a smart idea.'"
It turns out, Hayhurst was keeping track of his teammates.
Hayhurst's second book, "Out of My League," which chronicles his 2008 season in San Diego's system, hit stores last week. Carlin, who was teammates and roomates with the pitcher turned best-selling author that year with Triple-A Portland, is prominently featured throughout the non-fiction story.
The book is a follow-up to Hayhurst's first book, "The Bullpen Gospels." Both stories detail the pitcher's climb through the Minor League ranks as a non-prospect, shedding light on what life is like behind the scenes for players who are stuck dreaming about reaching the Majors. The stories show the balancing act of playing baseball, maintaining relationships and trying to pay the bills on often meager pay.
Carlin, who has read both books, feels Hayhurst has done a great job of telling what life is really like during a player's often unglamorous rise up an organizational ladder.
"He talked about some really cool things that fans might not see," Carlin said. "There's definitely the dynamics of the clubhouse, the travel, the thought process, the interaction with the coaches. He captured the things that you don't see as fans. Everybody thinks we've got it made here.
"They just don't realize that there's no job security, and it's a high-stress job, and you don't make a lot of money until you get to the big leagues. It's not easy. I thought he did a good job conveying some of that stuff."
Carlin can appreciate Hayhurst's storyline because they have followed similar career paths.
The 30-year-old Hayhurst began his pro career as a pitcher for Class A Eugene, where he was first teammates with Carlin in 2003. Hayhurst has spent eight years in the Minors with only a brief taste of the Majors with San Diego in 2008 (he posted a 9.72 ERA in 10 games) and with the Blue Jays in 2009 (2.78 ERA in 15 games).
A right shoulder injury cost Hayhurst the 2010 season and, after spending last year with the Rays' Triple-A affiliate, the pitcher is heading overseas to pitch in Italy this summer.
Carlin, 31, has spent the past 10 years mainly in the Minors, though he has had short stints with the Padres (2008), D-backs (2009) and Indians (2010). This spring, Carlin is fighting for the chance to be Cleveland's third-string catcher, meaning he likely has a ticket to Triple-A Columbus in his future once again.
Cleveland has its big league catching tandem locked in with starter Carlos Santana and backup Lou Marson.
Carlin could have looked for a job with another organization as a Minor League free agent this past winter, but he chose to re-sign with the Indians. Part of the reason was the Indians' brass told Carlin they much appreciate the things he does for a team that do not show up in a box score, such as helping groom young pitchers.
"I think that was one of the big reasons I signed back," Carlin said. "I knew that they wanted me. I have good relationships with the staff. It's nice to go somewhere that you know that you're wanted. I knew coming in that I'm not going to be an everyday guy in the big leagues. I was disappointed I didn't get an opportunity last year.
"That being said, I didn't have a great year last year, personally, on paper or whatever. But, last time I was in the big leagues, I performed and I produced. They've already seen me do it, and I'd expect that they think I can do it again."
Carlin's first taste of The Show came during the 2008 season written about by Hayhurst in his new book.
When Hayhurst finally gets his call to the big leagues, the pitcher was promoted to start in place of Greg Maddux, who had been traded to the Dodgers that August. On the day that Hayhurst arrived in San Francisco to meet up with the Padres, he ran into Carlin at the team's hotel. As fate had it, Carlin was being sent back to Triple-A that same day.
That was one example of how Carlin's story of baseball survival has mirrored Hayhurst's at times.
Carlin was along for much of the ride that takes place in "Out of My League," and the catcher peppered Hayhurst with phone calls while reading the book.
"It was a little funny," Carlin said, "just because I was there for so many of the events that he talked about in the book. He captured all the details. Reading it, it was like, 'Oh, yeah, I remember that.' And then I couldn't help but call him right away and say, 'Do you remember this?' Or, 'What about that?'
"It was really cool. Some of the stuff -- obviously, the first call-up and stuff like that -- are things you'll never forget. It was just kind of cool to see his perspective on that sort of stuff."
The two have become good friends along the way.
"When I first met him, I didn't like him at all," Carlin said. "I thought this guy was a dork. And he was, but he was more mature than most of us. He just had a better perspective on things than I did at that time. Dirk's kind of always been Dirk.
"But, to see just that transition from Minor Leaguer to big leaguer, and then going back and forth, there's a maturation process that happens there. It's just cool to see how he captures all those thoughts on paper."