Before that season-ending injury, the 6-foot-1, 202-pounder had seriously considered playing college football.
"A lot of people were trying to talk me into it," he said. "I was kind of in the middle. I didn't know whether I was better at baseball or football."
After weighing the options, Marson pursued baseball full-time, also giving up playing basketball in the winter to rehabilitate for the spring campaign on the diamond.
"I realized I had a way better chance at baseball as far as my future goes," Marson said. "[Football's] something I closed the yearbook on. I was going to go play, but when I got hurt I realized I wasn't the prototypical 6-foot-4 quarterback like kids today. I think the injury was a blessing in disguise."
Marson was selected in the fourth round of the 2004 Draft by Philadelphia and decided to sign instead of going to college -- partly because he was new to catching, so he would most likely bench-warm behind a more experienced collegiate player, whereas he'd get an opportunity to play every day in the Minors. And partly because nobody called him.
"No colleges really followed me," Marson said. "Not until two weeks left in my senior season did the University of Arizona and Arizona State finally call. They were like, 'How come you haven't signed with anybody?' and I said, 'Nobody called me.'"
One person who did call was Reading manager P.J. Forbes -- into his office on June 26, 2008 -- to tell the fifth-leading hitter in the Eastern League he would be playing at Yankee Stadium in the 10th annual XM Satellite Radio Futures Game on July 13.
"He reacted as only Lou Marson could," Forbes said. "Calmly saying, 'Oh, that's cool. That'll be a lot of fun.' He takes everything in stride and is a real even-keel guy. The good thing about that is you can also see the fire in him."
Marson won't be alone in the Big Apple, as three of his teammates -- Carlos Carrasco, Jason Donald and Greg Golson -- were also chosen as part of baseball's next standout crop of athletes. Both Golson and Carrasco have been teammates of Marson's since 2004, meeting one another as members of the GCL Phillies.
June 26 also happened to be Marson's 22nd birthday. At 22, he's the second-youngest player (to Carrasco) in Philadelphia's upper Minor Leagues. It's the fifth-year pro's youthful experience that makes him so unique in Forbes' eyes.
"He's one of the most mature hitters I've seen for his age, and he doesn't just give away at-bats," Forbes said. "That's pretty special for a guy his age playing his first season of Double-A ball."
One June 18, Forbes moved Marson -- who said he's hoping to bring 13 family members to the Futures Game -- into the cleanup spot on the heels of a six-game hitting streak. In 71 games, Marson is hitting .324 with 39 runs, two home runs, 39 RBIs and an on-base percentage of .442 (third-best in the Eastern League).
With a team-high 51 walks -- 17 more than the next closest R-Phil -- Marson's plate discipline is one of his many heralded attributes.
"I try to see as many pitches as I can," said Marson, who's watched multiple Futures Games in the past. "Eventually as I get older, I still want to do that. Sometimes I foul a pitch off, then I'll get it again and I won't miss it. I think as I mature more, I'll start hitting that pitch more often. I think that's what makes a great player."
Still, being that he's only caught since his junior year of high school, Marson's game isn't flawless. In mid-May, he was having severe trouble throwing runners out. As of July 1, though, Marson had gunned down 27 of 67 base runners attempting to steal for a 40.3 percent clip, good for fourth-best in the Eastern League.
"Instead of going forward, he was coming up and missing high a lot," Forbes said of Marson's throwing troubles, which could be a residual effect of his quarterbacking career. "He's been throwing the ball a lot better lately. For me, that's not a big concern. Watching him come out and make throws, I think he can handle it at the next level."
One thing Marson can certainly handle is his on-field demeanor. Forbes said his backstop knows the appropriate way to discuss questionable calls by umpires without ruining his next at-bat, as well as how to control on-field situations when things turn sour. Forbes allows Marson to call every game himself, with the occasional suggestion from the dugout.
"For being a first-year guy here and only being 22, he carries himself very well," said R-Phils pitching coach Tom Filer. "It's great because you don't often see a young player handle themselves like he does in tough situations."
Though Marson jokes about making a Russell Martin-like move to third base (a former Minor Leaguer who was chosen to play in the 2005 Futures Game), one of the Phillies' biggest needs is a long-term catcher, and both Marson and Forbes think that's well within the realm of possibility.
"This is my third full season and it's starting to click for me," Marson said. "Hopefully I can continue to be successful for the rest of the year. My goal coming into the season was to get a September call-up. That's not in my hands, but hopefully."
"For me, he's an everyday big-league catcher at some point, whether it's this year or next year," Forbes said. "Special players do special things. He's become a good student and that's what it's going to take because every level he goes to, it's going to be a learning process."
Marson's next course begins July 13 in New York.