When he walks through the school's hallways in his lacrosse uniform, people frequently call him "Coach," although Brunner is not your ordinary freshman — and he's not a coach, either.
He is, however, big — 6- feet 7 and 322 pounds — and a force to be reckoned with on the field.
Moreover, at 40, Brunner is twice the age of many of his Cardinal teammates.
Middle-aged and multi-talented with a lacrosse stick, the father of three sons, Brody, 6, Bailey, 10, and Tiernan, 12, leads the team in goals with 30.
"The kids love him and he loves the kids," CCBC, Catonsville coach Bill Zopp said.
When Zopp found out Brunner was taking classes that would help him get a Master's degree, the coach invited him to play for the Cardinals.
Brunner's sizable impact already has opposing teams game-planning to stop him.
When the Cardinals went on the road to face County College of Morris, N.J., earlier this season, rival players who dubbed Brunner "Sasquatch," implemented an unconventional defensive alignment geared toward keeping his production to a minimum.
"The guy locked me off the whole game," Brunner said.
It worked, sort of, though his teammates picked up the slack in Catonsville's 8-4 victory, the first win of the season after three straight losses.
On April 11, in a 16-15 home victory over Delaware Tech, the Lutherville resident took over the game.
He scored seven goals, including the game-winner with 30 seconds left on a behind-the-back shot off a feed from Catonsville High graduate Greg Abendschoen.
In the first half, Brunner had a stretch of four goals in just 2:04, including two in six seconds that helped the Cardinal erase a 5-2 deficit.
Abendschoen also assisted on one of those, but the game-winner was special.
"It was really the only angle he had," Abendschoen said. "I was excited for him."
Abendschoen first saw Brunner at a pre-season meeting.
"I figured he was going to help coach the team," Abendschoen said. "I was shocked when I heard he was playing."
Brunner does coach his sons on the Lutherville-Timonium Recreation and Chesapeake Rock club teams, which gives him insight into the game that benefit his younger collegiate teammates.
"He's almost like having a coach on the field," Abendschoen said.
The player known as "Big Mike," is happy just being one of the guys when it comes to following his coach's instructions.
"He yells at me just as much as any other kid," Brunner said about Zopp.
Zopp and assistant coaches Ralph Quillen and Matt Enoch played with Brunner on the Re/Max club team in the Maryland Masters Lacrosse League.
Brunner, who was cut from Loyola's lacrosse team as a freshman and from the basketball team as a sophomore, played three years of collegiate basketball, one at CCBC and two at Albright College in Reading, Pa..
Neither stint counted against his junior college lacrosse eligibility.
"The main focus initially wasn't to play lacrosse," Brunner said about enrolling at CCBC-Catonsville to take courses that will eventually lead to Master's degrees in math and special education. "It was really just to get back to school, so I could get a high-level coaching job. Playing lacrosse was a bonus."
At the time he made the decision to train for the team tryout, he weighed 360 pounds.
In January, he sent his coach an email to make sure he was still wanted.
"I said, 'If I'm not going to help your team and be a plus, don't keep me on the team as a charity case,'" he recalled. "We planned to see how it would work and, unfortunately, he lost a couple of his good kids to grades — and the rest is history."
Brunner scored two goals in his first game, an indication, he said, "That I could play with these guys."
A real estate agent who takes four classes at the school, the busy Brunner also owns The Salon at Mays Chapel, run by his wife, Michele.
He's just as industrious on the field as he is off it.
"We've adapted our offense, not completely around me, but there are a lot of plays that do focus on me. Luckily enough, I've got enough stick work, if I can get a (defender) on my hip, I'm open."
Brunner utilizes his size and vast lacrosse knowledge to offset a lack of speed.
"I'm not going to outrun anybody, it's the positioning and timing of the cut," he said.
Brunner, who is right-handed, takes most of his shots left-handed because that's the way he learned to shoot from older brother Matt, who, with his other brother Greg, played lacrosse at Loyola.
"He's just a workhorse," Zopp said. "He catches and shoots 100 balls a day in practice.""
Brunner's main focus now is to get the team winning consistently and make a strong postseason run in the Region XX tournament
"You play the game to win and you always want to get as far as you can," he said. "There are some really good kids on this team that this might be their last time they will play college lacrosse."