The 27-year-old catcher, a 2006 graduate of the Naval Academy, refuses to give up on his dream of playing in the big leagues. But first things first.
Johnston served the better part of the last three years in active duty with the Navy, so this offseason he participated in the California Winter League, a pay-to-play operation where most of his league-mates are hoping to catch a scout's eye.
"My scout, Craig Weissman, told me about the league," Johnston said. "Obviously, from not playing for a couple of years, I wasn't going to get into a major winter league, and this was the best opportunity to get ready for spring training . . . I'm feeling just like I did when I stopped playing."
Unlike his winter teammates, Johnston already has a pro contract. The Athletics selected him in the 42nd round of the 2007 draft and signed him the following February.
Originally, he intended to both play baseball and serve in the Navy reserves. After all, Johnston spent nearly two years on active duty before even signing with Oakland.
He made his pro debut in 2008, playing in 36 games for low Class A Kane County. But then the Navy called him back into active duty that June, putting his baseball career on hold.
For a time, Johnston served on the USS Curts, a frigate that protected vessels off the Somali coast. In one heated moment, he and his crew helped deflect a pirate attack on a Singaporean vessel in the Gulf of Aden.
Now, Johnston prepares for new battles in spring training camp. He knows that making one of Oakland's minor league clubs, most likely as backup catcher, will be no easy task.
Improving the odds, farm director Keith Lieppman liked what he saw of Johnston three seasons ago.
"The thing we noticed about him was that he had excellent tools," he said. "He ran well, threw well, had good skills behind the plate. He showed some power in batting practice.
"He didn't have much of an opportunity to develop, but we felt the tools were there."
Johnston grew up in Trenton, N.J., and was a non-prospect as a 160-pound high schooler. At Annapolis, he grew to 6 feet and about 200 pounds, and his skills grew with him.
• The A's expect catcher Ryan Ortiz to be ready to open the season after missing half of 2010 to shoulder surgery.
• Mike Henriques, Oakland's new minor league strength and conditioning coordinator, worked previously with the Padres and with the NBA's Portland Trail Blazers.