"My brother, he was the one with the work ethic, and he worked 100 times harder than I did ever in high school and throughout college," Justin admitted.
So on this particular morning, Matt was up at 6:30 a.m. as usual.
"I remember thinking, 'This guy's an idiot, I'm getting my sleep,'" Justin said.
But Tammy had enough.
"She said, 'You're going to start waking your butt up and go work out with your brother or you're going to get a job. You're not going to be lazy all summer,'" Justin said, recalling the conversation.
Now, Tammy Grimm is a teacher, and she was working two jobs. That morning, she drove Justin to the school. The timing was perfect as baseball coach Mark Daniels was walking out of the school as they pulled up.
"She said, 'You need to talk to my son, and you need to get him here and tell him he needs to working out because he thinks he's Tom Glavine, Greg Maddux and John Smoltz all rolled into one and he doesn't have to work,'" Justin said.
Said Tammy: "Poor Coach Daniels probably thought I needed medication. I just got in my car and drove off."
What she didn't find out until last year is that Justin and his coach had a long talk.
"It was only last year that Justin finally told me what Coach Daniels talked to him about, that he had the abilty to go pretty far in the sport, but that he was going to have to work at it," Tammy said. "[Daniels said] even though Justin had talent, if he didn't work at it, it would be wasted talent. From that morning forward, when my oldest son, Matt, would say, 'We're going for workouts,' Justin was up and ready to to go."
On Mother's Day, Justin, 25, wanted to say thanks to his mom for giving him the timely push.
"I definitely wouldn't be where I'm at today -- technically, I learned from my brother, but my parents supported me and got it kick-started," Justin said. "It surprised me -- my mom came in furious one morning and said, 'Get up, we're going.' She jerked me into gear."
Justin had made it clear to his mother and father, Mark, that he was going to pitch in the big leagues. In 1999, he announced his decision because of another Bristol, Tenn., native, Jimmy Gobble, who was the Royals' first-round Draft pick that year. Gobble stopped by the local Little League field before leaving for the Minors and saw Justin throw a one-hitter to beat Gobble's former team.
"Jimmy was signing balls and things like that for the kids and Justin got a ball and that night, that's when he said, 'I want to be a professional baseball player when I grow up,'" Tammy said. "We were like, 'We'll see.'"
When your mother is a teacher, it's understandable that there's more emphasis placed on education than baseball. So when Grimm met with his high school guidance counselor to discuss college and his major was baseball with no Plan B, the counselor called Tammy in.
"The guidance counselor looked at my mom, and said, 'We're trying to talk to him about a Plan B, and all he can tell me is he wants to play baseball and I'm trying to get something out of him and I can't,'" Justin recalled. "My mom said, 'We've had this talk at home, and that's all I get out of him, too.'
"My mom gave me more support than anything," Justin said. "My dad was a big sports guy, and he was the guy I went to talk to about problems, but my mom, she helped keep things in perspective and was always there for me."
Justin was selected in the 2007 First-Year Player Draft by the Red Sox, but he did not sign and got a scholarship to Georgia. In 2010, he was selected in the fifth round by the Rangers and signed in August that year. Last July, he was one of four players the Rangers sent the Cubs in the Matt Garza deal.
Did Grimm ever come up with a Plan B?
"Honestly, I did not," he said. "Georgia was my Plan B. I didn't think I'd have to put it into use. My mom, being a teacher, she was all about education. Me, since I had the scholarship, I don't think she worried about it too much."
Said Tammy: "He may not think of [Georgia] as Plan B, but it was Plan B."
Grimm is one year shy of completing his degree.
"I'm always asking him and trying to encourage him and see if he can't get those last few classes finished up and get that degree," Tammy said.
His major? Consumer economics. It was based on a suggestion by his mother, who wondered out loud what he was going to do with his signing bonus.
In April, Tammy was at Wrigley Field, bundled in a Cubs sweatshirt and wearing team-themed earrings to cheer her son in a series against the Reds.
"I was really excited, and he did well, so that always makes a mama happy -- when their child is doing well and helping the team out," she said. "I still get excited when he runs out there, whether it's from the bullpen or as a starter and gets an opportunity to play in these big league games."
Last year on Mother's Day, Justin sent Tammy a baseball and signed it: "Thank you for everything, you're the best mom in the world." It's still on the mantel at the family's home.
"She's really been great," Justin said. "She's definitely had her times of being very irate with me, but when you get to this point, you realize why she did what she did. Not many people get it at the time. She was always good at pushing but didn't push too much."