Playing in the Grapefruit League for Toronto was the first time the catcher had left his comfort zone — a quiet, defensively sound place with the Los Angeles Angels for the first seven seasons of his career.
Mathis couldn't have imagined that roughly 365 days later, the same spring clubhouse would be bolstered by big names like Jose Reyes, Mark Buehrle and Josh Johnson, and that he wouldn't be a part of Toronto's new status as a contender in baseball's most rigid division.
Barely three months after signing a two-year extension worth $3 million to stay in Toronto, the veteran backstop was dealt to Miami in November's 12-player blockbuster trade.
"It was (a shock)," he said. "I thought I was going to be in Toronto for at least two more years."
As the Blue Jays roster was enriched with top-level talent in the off-season, the 29-year-old is across the state at the Miami Marlins' spring home in Jupiter. It's his second new beginning in as many years.
The superstars have gone north, and Mathis is the fifth-oldest player on the 40-man roster.
"Baseball is a crazy game," he said. "You never know where you're going to be from day to day, and that's kind of what happened."
Mathis was a pitcher favourite on the Angels staff, well-liked for his defence and game-calling, when he was traded to Toronto at the end of 2011.
"I had mixed emotions going into it — a different country, my first team other than the Angels — but I had a good time," he said of his brief stint in Toronto. "The city was great, the people were great, I enjoyed playing in the AL East. It was a good experience."
Under the Rogers Centre roof, Mathis spent a lot of time on his struggling offensive game with Blue Jays hitting coach Dwayne Murphy. In 71 games as Toronto's backup catcher, he enjoyed the highest average of his career in a full season at .218.
With his confidence elevated, he chipped in more home runs than his previous two seasons combined.
"It was a lot of hard work ... in the cage with Dwayne Murphy," he said. "We related pretty well. Some things that he was saying made a lot of sense and it made its way to the box in my approach. I feel like I had a better year, and I felt a lot better at the plate once I was in there."
Mathis boasts a subpar line at best. He's just a .198 career hitter, but his loyalty and defensive skill set were the elements that nearly quashed the massive Toronto-Miami trade. He was the final piece, a player Jays general manager Alex Anthopoulos was reluctant to give up.
"I heard something like that, but you never know," Mathis said. "In those kind of deals, in any deal, you just don't know when there's rumours floating around."
Mathis turned four more double plays and caught just two fewer base runners than his Blue Jays counterpart in J.P Arencibia. The Toronto starter played 268 innings more than Mathis.
But Mathis has had a rough start to spring training. He sustained a broken collarbone when Cardinals outfielder Matt Holliday fouled a ball off of his chest protector in the Marlins Grapefruit League opener on Feb. 24.
His job is defined by mobility and quick reflexes, but Mathis finds himself thinking about every small movement from turning around, to grabbing things to opening his mail.
Earlier this week in the Marlins clubhouse, he was excited to see a FedEx package sitting on the stool underneath his name and number.
When he realized he had coffee in one hand and the other confined to a sling, he lost interest.
"With my legs, I could probably get it done," he said of trying to get the package open.
His injury is a setback for a young Miami team trying to prepare for the season. Mathis is the only catcher with major-league experience other than 23-year-old starter Rob Brantly, who only has 31 games under his belt.
He doesn't see himself as much of a leader, but he's already made the rounds to let the younger catchers know he's all ears.
"This, that, or the other, don't be afraid to ask," he said.
Despite the injury and the lingering disappointment of being traded, the Marlins clubhouse is starting to feel like home for Mathis.
"I like the attitude of all the younger guys," he said. "Everybody's hungry. Not to mention, everybody's been really good people.
"It means a lot when you come in as an outsider."