But a hip injury to Joe Flacco suddenly put the fleet-footed first-round pick on the fast track.
Now, Jackson not only is suiting up for a postseason game in his eighth career start, he's making NFL history: He will become the youngest quarterback ever to start an NFL playoff game.
The fact he will be the first quarterback to start a playoff game before his 22nd birthday has seemed to impress everyone except Jackson himself.
"I’m here to play football. I was 21 all year,” Jackson said. "So, it’s another game for me."
Jackson will start Sunday’s wild-card game between the Ravens and Los Angeles Chargers at 21 years, 364 days. He will surpass Bernie Kosar, who was 22 years, 40 days old when he started for the Cleveland Browns and threw his first touchdown pass in a 1985 postseason game to Ozzie Newsome (who drafted Jackson 33 years later).
Young quarterbacks have recorded mixed success in the postseason. Since 2001, only four quarterbacks 23 years old and under have won a playoff game (Michael Vick, Ben Roethlisberger, Flacco and Mark Sanchez). Over that span, quarterbacks 23 and younger have a 10-11 record (.476) in the postseason.
Jackson shows his youthful exuberance on the field, from dancing in the huddle to somersaulting into the end zone. But the Ravens don’t think too much about Jackson’s age. Players and coaches have praised Jackson for his poise in going 6-1 as a starter this season.
"Lamar’s maturity has impressed me greatly,” coach John Harbaugh said. "Players see it when he walks around. He’s very comfortable with who he is. That’s a sign of maturity, for sure.”
In comparison, Jackson will be making his eighth career start, while Chargers quarterback Philip Rivers will be starting in his 10th postseason game.
When Jackson and Rivers, 37, square off, it will be the third-largest age gap between starting quarterbacks for an NFL postseason game, according to the Elias Sports Bureau. Jackson was only 7 years old when Rivers threw his first NFL pass, against the Kansas City Chiefs on Jan. 2, 2005.
But Jackson appears unnerved by his whirlwind season. At this time last year, Jackson was playing in the TaxSlayer Bowl. He's now three wins from reaching the Super Bowl.
"It’s just a name -- ‘the playoffs,'" Jackson said. "You’re trying to get the championship now. It was for us to get in it, and we’re in it now, so we want the big thing. We want the big thing now."
Jackson has been the key to the NFL's most dominating rushing attack since the middle of November, and he has done enough in the passing game to win. Harbaugh had the opportunity to go back to his Super Bowl-winning quarterback on Dec. 12, when Flacco was medically cleared to play again. But he stuck with the more inexperienced but hotter hand in Jackson.
"Every single game he's definitely getting a little bit more calm, more confident in what he does," Pro Bowl guard Marshal Yanda said. "Young guys have a chance to grow in every single game, and I think he's done that."
It is believed that Michael Vick is the youngest quarterback to win an NFL playoff game. Vick was 22 years and 192 days old when he won at Green Bay.
The last time the Ravens went with a rookie in a playoff game was Flacco in 2008. Flacco, who was 23 at the time, led Baltimore to the AFC Championship Game that season.
"In the NFL," wide receiver John Brown said, "age don't mean nothing if you can play."
Jackson turns 22 on Monday, a day after his first playoff game. He knows what would make the best gift.
"That win, I can taste it,” Jackson said. "Just like Thanksgiving, with that food and sweet potato pie. I’m trying to taste that victory for my birthday Monday.”