"The name is a lot to live up to here," Johnson said. "Since I've been here, all I've heard is about the other Dennis Johnson. Everybody says he was really a nice player and that I have to live up to that. It's a little bit of pressure, but I know what I have to do. He did his part. Now it is my turn."
The Kentucky junior linebacker knew who the other Dennis Johnson was when he came here.
"I was actually watching the (NFL) draft because I am a big football fan. I saw him get drafted," Johnson said. "That's when I saw he had the same name as me. I remember he was a tall, lanky kid and I remember them saying on TV that he bench pressed 225 pounds 17 times. I remembered all of that. Then when I got here, I saw his name and picture on the (practice facility) wall for his season and career sacks records."
Sometimes people here are surprised when they hear his name.
"They actually believe I am the other Dennis Johnson. They say, 'You look bigger on TV,'" Johnson said. "Then I have to tell them I am the other Dennis Johnson."
The path to UK was not an easy one
He did not have an easy path to Kentucky and becoming a probable starter in the season opener at Louisville.
After graduating from Vicksburg (Miss.) High School, he went to Valley Forge because he had family in the area. He was a 215-pound defensive end, but he had 55 tackles and 16 quarterback sacks his first year.
"All the big schools came in, especially those in the Big Ten. But Auburn and Kansas State looked, too," Johnson said.
He figured his future was secure. Then at the start of his second season, he was moved to linebacker because a teammate was injured. He had 45 tackles and eight more sacks. But once he started visiting schools and coaches saw he was only 6-feet tall, the recruiters backed off.
"They said I wasn't tall enough to play defensive end," Johnson. "I really didn't have a chance to showcase myself at linebacker. I was out to dry."
Then his junior college coach called UK offensive line coach Paul Dunn. Johnson eventually was offered a chance to become a walk-on player and quickly accepted.
He had toyed with the idea of going to Colorado State, but the school didn't offer the communications program he wanted.
"The way I look at it, it's school first, then football," Johnson said. "Football may not always work out, so I have to think about life after football. Kentucky has a good communications program, so here I am.
"If I want a good job after graduation, I had to take out loans and keep going. That is driving me to do this. I'm in the hole (financially). I went from the top to the bottom just because coaches thought I was too short. I had to prove myself all over again."
He's done that. Johnson impressed defensive coordinator Mike Archer last year, when he was being redshirted, with his playmaking ability at outside linebacker. He was moved to inside linebacker in the spring and despite making mistakes as he learned the new position, he again impressed Archer.
Now with Williams likely out for at least the first game with a hamstring tear, Johnson could become a starter and bring a new dimension to UK's defense.
"He's a difference maker because he can run and chase people down," Archer said.
The UK defensive coordinator said last year's inside linebackers - Williams and Chad Anderson - were "thugs" who used their size inside to make plays but had trouble making plays on the perimeter. Johnson's speed will enable him to do that.
"Dennis can get around people," Archer said. "He'll give us more flexibility with our blitz calls and will give us a pass rushing threat we didn't have last year."
Johnson knows he has to learn not to be so aggressive that he takes himself out of plays, a point Archer stresses every practice.
"The more practice I get, the more plays I'll learn to make and I'll learn what to do, and not do," Johnson said.
His brother plays for the Atlanta Falcons