He became a starter midway through last season, when the Rams won their third consecutive state title. This year, Theckston is a senior leader for a team that is 13-1 and ranked No. 1 in South Jersey by The Inquirer and No. 1 in the state by the Newark Star-Ledger entering Sunday night's showdown with St. Joseph of Metuchen at the Diamond Nation complex in Flemington, Hunterdon County.
"As a pitcher, your success stems from your catcher," said Gloucester Catholic senior Mike Shawaryn, a Maryland recruit who has been tracked by dozens of major-league baseball scouts this spring.
"Jon has done a great job behind the plate making us looking good."
Shawaryn calls Theckston a "mini-manager" because of his ability to control the game.
Gloucester Catholic coach Mike Rucci, a former catcher for the Rams and Rowan University, said Theckston has been instrumental in the team's strong start.
"He's exactly what you look for in a catcher," Rucci said.
Theckston is batting .321 with four RBIs. Fittingly, given his unflinching approach, he has been hit by a pitch four times, tops on the team.
"He's not going to hit .600," Rucci said. "But he's a tough out, especially in big situations."
Theckston's defense is his strong suit. He has thrown out 10 of 12 would-be base stealers.
"That's my favorite part of the game," said Theckston, who plans to attend Rutgers-Camden and play for former Gloucester Catholic coach Dennis Barth.
The Rams have an imposing array of pitchers. Shawaryn, a righthander, leads with a 3-0 record and a 0.00 ERA. He has struck out 30 and walked just four.
Sophomore righthander John Murphy is 2-1 with a 0.38 ERA. He was one strike from his first no-hitter Wednesday and settled for a one-hit masterpiece in a 2-0 victory over Delsea.
But the team also features juniors Mike Mercer (1-0, 1.31 ERA) and Steve Mondile (1-0, 3.68), sophomores Dante Scafidi (1-0, 0.00) and Matt Parr (2-0, 1.31), and freshman Tyler Mondile (2-0, 0.40).
"Every person, from freshmen to seniors, we believe they can do the job when they take the mound," Theckston said.
But the catcher says all pitchers are different, too.
"Some kids are angry out there and you have to kind of baby them a little bit," Theckston said. "Some are a little lackadaisical and you have to try to get in their heads a little bit.
"I'll do whatever I have to do to get the best out of them. I'm an experienced catcher, and it's my job to be a leader out there."
Talent goes a long way. But the best teams tend to have less-gifted athletes such as Theckston, a program player who worked his way through freshman and junior-varsity ball and into the varsity lineup.
The dues that Theckston paid carry a lot of weight in the dugout and on the field. He brings grit and a grinding, every-play, everyday determination that defines the Rams as much as those live arms.
"The thing with Jon is how hard he has worked since freshman year to get as good as he is now," Shawaryn said. "Every outing, I know he has my back."
Contact Phil Anastasia at email@example.com. Follow on Twitter @PhilAnastasia. Read his blog, "Jersey Side Sports," at www.philly.com/jerseysidesports