The 6-foot-4, 220-pound Greenard said he knows prior to the weekend the word was Kentucky lead for his commitment.
But on Sunday night, before leaving U of L's campus he committed to the Cardinals. He picked U of L over Kentucky, Miami, Ohio, and others.
"Mainly I was stuck on Kentucky because I had been on campus before but I hadn't been to Louisville campus," he said. "I think that's why everybody thought I could end up at Kentucky.
"But now that I've had a chance to see the campus and facilities and meet the coaches it just all blew me away. Everything was just great and I am so excited to make a commitment."
Greenard said he had a long chat with Grantham and went through some drills at camp to help seal the deal in his mind.
"He sold me on what I could be in their defense," Greenard said. "He talked to me about the 3-4 and said I could be a standup outside guy and would be rushing the quarterback, just getting me active."
Greenard said he "didn't know it would be this good," talking about the visit to U of L.
"Of course, I had heard nothing but good things about Louisville," he said. "I was anxious to get there and it was so much better than I expected. Just a combination of everything, the facilities, the dorms, the food places and just how everything is right there. I loved it."
Grenard said Grantham is "so well known because of his resume," in Georgia and that played a factor into his commitment.
"He's a great coach and his resume speaks for itself," he said. "I am very excited. I know the recruiters won't stop, but it would take a lot to even make me think about anywhere else."