WESTFIELD -- Ronnie Harrison Sr. lined up in a free safety spot he stepped into for the first time just a few days ago. It was time for another live team drill, one of the first of the year with the pads on, and suddenly the 27-year-old was leaving that new post and inching closer and closer to the line of scrimmage.

The ball was snapped and Harrison exploded off the right edge. He caught the whole offense by surprise, zipping through unblocked into the face of Colts quarterback Anthony Richardson, who tried to throw over him, only for Harrison to reach out his left arm and swat the ball back into a row of teammates who greeted him with "oohs" and "aahs."

This is Harrison, reimagined as a free safety.

The last time he played this position, Richardson was playing youth football on a grass field in Gainesville, Fla. Gus Bradley was trying to scheme the Seahawks' "Legion of Boom" secondary to a repeat Super Bowl title. And Andrew Luck was leading the Colts on a run to the AFC Championship Game.

It last happened his senior year at Florida State University School, back when he was a four-star recruit and Nick Saban had just secured his commitment. The greatest coach in college football history saw something different in him then, a heavy hitter at strong safety who could add another enforcer in the box.

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And so that's the direction Harrison went, becoming a third-round NFL Draft pick and a player for the Jaguars and Browns who started 45 games and a playoff game at strong safety.

But here he is, four days into his seventh training camp, subbing in as a first-team free safety each day.

"I definitely was a little surprised," Harrison said.

Nick Cross starts team drills at that spot, but after a series or two, Harrison checks in alongside Julian Blackmon for a role that fluctuates between playing in the box and living in space as the last line of defense.

"When Ronnie gets in there, it seems like something good happens, whether he's playing linebacker or he's playing strong safety," Bradley said. "We thought, you know what, we've got this competition back there. If something good does happen, let's take a look at it.

"He's got the skill set needed to play that, so we'll give him an opportunity to compete with the rest of them."

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Just one year ago, Harrison was a free agent for the second time in his career and his phone wasn't ringing. Only the Ravens were offering a tryout.

Then the Colts called with an offer -- but only if he'd move to linebacker.

"I kind of didn't know how to take it because I've never been at linebacker," Harrison said. "I was kind of down about it."

But without other options, Harrison put his head down and made the transition work, sticking on the practice squad for several weeks and then getting the elevation when the Colts needed a replacement for Shaquille Leonard. Harrison became a starter at the "SAM" spot in base defenses and corralled interceptions in two of his first three games.

Then Blackmon injured his shoulder, and the Colts asked Harrison to play his old position for starts against the Raiders and Texans.

After the Colts fell just short of the playoffs, they made it a priority to bring Harrison back. They just weren't sure quite where yet. Then the draft arrived, and they spent a fifth-round pick on Missouri safety Jaylon Carlies with a plan to move him to linebacker.

That's when they asked Harrison if he wanted to move back to safety full-time.

"The free still has to be really aggressive," Harrison said. "You still have to make tackles in the open field. You have to be reliable on the back end. You have to know the defense and be a shot caller."

Now, the pads are on and the pressure will ramp up. Harrison is competing against Cross, who is trying to take a Year 3 leap and regain the trust he lost as a rookie starter; and Rodney Thomas II, who is trying to bounce back to his rookie year form.

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They all have to prove something because two Pro Bowl safeties remain on the free agent market. Justin Simmons and Quandre Diggs combine for five Pro Bowls, and they appear to be waiting out the right fit in training camp. The Colts are monitoring both, and the safeties on their roster know it.

"We're all fighting for the same spot," Harrison said. "Whenever I get the chance to go to free, I'm trying to show them I know what I'm doing. I know how to line up. I can make the plays. I can be in the right spots.

"That's the sense of urgency you have to have."

Contact Nate Atkins at natkins@indystar.com. Follow him on Twitter @NateAtkins_.

This article originally appeared on Indianapolis Star: Ronnie Harrison Sr. has entered the Colts' free safety competition