Isaiah Johnson has been playing football for 15 years. He went 13 straight years without getting hurt. When injury struck the Georgia Tech safety at the most inopportune time, the wait was insufferable.

Nineteen months removed from a devastating knee injury, however, Johnson is ready to take the field and re-establish himself as a leader in the Yellow Jackets' defensive backfield. Georgia Tech opened fall camp Thursday, and the countdown to Week 1 and return to meaningful action for Johnson is within a month.

"Oh, I'm past 100 percent," Johnson said with a laugh. "It's been a year-and-a-half — what have I been doing? I'm good. I went through spring practice and it was good. After that first day, it was just back to normal."

Johnson had a difficult time adjusting after tearing both the anterior cruciate ligament and lateral collateral ligament in his left knee in a bowl practice leading up to the Hyundai Sun Bowl against USC in December 2012. The 21-7 victory over the Trojans marked the first missed game of his career, snapping a 39-game playing streak — which included 26 consecutive starts — in his first three college seasons.

But the most difficult part might have come nine months later, with Georgia Tech's 2013 campaign already underway. Three games into the season, Johnson, who had missed spring practice, came to the conclusion with his coaches that he would be better off sitting out the remainder of the season, lest he risk further damage to a still-recovering knee.

"It was very difficult. I had to get it out of my system," Johnson said of the frustration. "But once I thought about it, [I] realized that this is the best thing for me."

"I've been playing football nonstop every year since I was 7, and 'til this point last year, I hadn't sat out a season, so it was hard for me and my family," the Tyrone, Georgia native later added, "because they had a whole football season [in which] they didn't know what to do, because they're used to watching me play."

Johnson said he stayed active by doing some light scout-team work during the season. He returned to practice this spring and was relieved to feel no hesitation breaking on balls or delivering hits to receivers. He said that the entire ordeal has only validated his love for the game.

"I think that it's been a work in progress for Isaiah," coach Paul Johnson said. "He was actually cleared last year but he just didn't feel right, so he wanted to make sure when he came back that he was completely healthy, and I think he's done that and I'm sure he's excited to play his senior year."

Isaiah Johnson led the team in tackles during his junior campaign, with 87 in 2012. And with safety Jamal Golden also returning after being granted a medical redshirt last season because of a shoulder injury, Georgia Tech will rely on its secondary to anchor the defense in coordinator Ted Roof's second season.

"Turnovers," Isaiah Johnson said when asked about the defense's goals, repeating the word three times for emphasis. "We want to lead the ACC and lead the nation or be in the top five, so turnovers, and being able to finish. We need to finish games."