Johnston's primary responsibilities include working with the hitters and catchers, teaching base running and recruiting. He will also serve as the third base coach and assist in running the Triton offense during games.

During the 2012 season, Johnston's instruction was instrumental in UCSD's offensive success and the all-around improvement behind the dish.

Following a two year hiatus from baseball as an officer with the United States Navy, Johnston returned to spring training with the Oakland Athletics in March of 2011. He started the 2011 season in Advanced Class A as a catcher for the Stockton Ports, hitting .318 with a .423 on base percentage.

In 2008, Johnston's first season of professional baseball, he batted .228 for the Low Class A Kane County Cougars before being called back to service with the Navy.

Over his four years as a Surface Warfare Officer, Johnston served on the guided missile frigate USS Curts and the amphibious assault ship USS Peleliu as Damage Control Officer and Gunnery Officer, respectively. He was awarded three Navy-Marine Corps Achievement Medals (NAM) and a Joint Service Achievement Medal. His first NAM was awarded for his efforts as the Officer of the deck in the thwarting of a Somalian pirate attack against the Singaporean merchant vessel, the Gem of Kirikae.

Johnston was a four year starter behind the plate for the Navy Midshipmen from 2003 to 2006. In his senior season he batted .317 with 51 runs, 27 RBI and 35 stolen bases. His leadership of the team and pitching staff resulted in one of the biggest turn arounds in Division I baseball history.

Johnston earned a Bachelor of Science degree in ocean engineering from the United States Naval Academy and finished his naval career as a Lieutenant.