A true freshman, Brown was put into the game against the University of Kentucky and recorded one tackle. But it wasn't his play Jean-Mary remembers.
"His eyes were as big as saucers," Jean-Mary said with a chuckle.
Brown, who has 94 tackles in 26 games the past two seasons, has gone from a wide-eyed youngster to a leader and star on the Cardinals' defense.
The 6-foot, 255-pound Brown is slated as the starting middle linebacker.
"He's getting that confidence, it's starting to brew in him," Jean-Mary said. "He's getting more and more vocal and just has confidence.
"He's really improved a lot. He's got a ways to go, but he's getting there."
Brown was the co-second leading tackler on the defense last season from the Sam linebacker position. He said he just want to get even better this season.
"I try and lead by example," Brown said. "We have all been in the system longer now, so we're all having better communication. I just need to keep working."
With only nine seniors on the roster, U of L head coach Charlie Strong said Brown is one of the juniors the staff will look towards for some leadership.
"Preston Brown, you look at him: he's big, he's 250 pounds," Strong said. "I always tell Preston, he's got to be the leader. You want the guy in the middle to be the leader, especially on defense, because he's the guy that's going to the calls.
"He's the guy that's going to the make the checks. He's the guy that does all the talking, so we've got to look to him for leadership."
Brown came to U of L out of Cincinnati Northwest and was ranked as one of the top 75 linebackers in the country as a senior. He had previously committed to Cincinnati but changed his commitment when Strong became the U of L coach.
And he hit the field right away.
Brown didn't start a game in 2010 but played in all 13 and had 10 tackles, including one sack, in his limited minutes as a youngster.
"With younger linebackers, you don't want to force-feed them and throw them into the fire before they are ready," Jean-Mary said. "Kids can lose confidence. But (Brown) is a kid who has gained a lot of confidence."
As a sophomore, Brown started 11 games and had seven or more tackles in seven games. He had a career-high of 12 tackles in the opener against Murray State and was named Big East Defensive Player of the Week on Oct. 31.
"I improved a lot," Brown said. "But I still knew I could get better."
Brown said he's in better shape and "really ready to have a good season." In the two practices, he was still at the Sam spot with freshman Keith Brown in the middle. But Jean-Mary said on Tuesday that Preston Brown was now in the middle.
"Preston's taken to the Mike backer position, he's kind of getting more comfortable and he's looking like a natural," Jean-Mary said. "Obviously with his size and his strengths, he would be the ideal fit and he's starting to kind of work into that role."
Brown said he's ready to take the next step and become the defensive leader, along with safety Hakeem Smith – who was the co-second-leading tackler a year ago.
"We lost two really good guys that were great leaders for us," Brown said. "Me and Hakeem and (Brandon) Dunn are trying to step up and be leaders. I'm in the middle, so I have to step up and become more vocal."
Jean-Mary said he thinks his play will also get better. He said the middle linebacker is supposed to be the best player on the defense.
"I think he's getting to that point where he can feel he could be a dominant player and wants to go show it," Jean-Mary said.