He is the mystery among a batch of safeties that is being examined in the days leading up to the season opener against the Dolphins. There isn’t any film of Barrett from the 2010 season; he spent the year rehabbing from shoulder surgery. Before last season he was with the Broncos, playing mostly on special teams.

Barrett may be an unknown, but he is part of a group that slid toward the edge of uncertainty when the Patriots cut veteran James Sanders and Brandon Meriweather in less than a week in meeting the league-mandated 53-man roster limit.

Coach Bill Belichick called releasing Sanders a tough decision. When it came to Meriweather, a two-time Pro Bowl selection, the coach said he just wasn’t in their plans.

“I think each year is a new year and I just don’t think you can pick teams, or pick your players, based on what’s happened in the past,’’ Belichick said. “You have to pick them based on what you think is going to happen this year, and that’s relative to the competition, to the makeup of your team, and players’ performance. All of those are obviously a part of it.

“Brandon played a lot of good football for us. We kept the players this year that we felt would be the best makeup for the 2011 team. It’s not the 2009 team; it’s the 2011 team, so those are the players that we’ve selected.’’

That 2011 look for the safeties now leaves Patrick Chung, in his third season, as the veteran. Chung has logged the most playing time in the group, starting 13 of 14 games last season and playing in all 16 games as a rookie. The other safeties include Sergio Brown, in his second year, and James Ihedigbo, who played mostly special teams with the Jets for three years and spent his rookie season on the team’s practice squad.

The changes must not take away from the overall production, Chung said.

“We’re going to work with the guys we have here, period,’’ Chung said. “Now we know who we’re going to be playing with, this is our family right now.’’

Barrett has joined that group. He originally was drafted by the Broncos in the seventh round in 2008 out of Arizona State. He spent the first 11 weeks on the team’s practice squad, but was promoted to the 53-man roster and started three games. In six games as a rookie, he had 22 tackles, four passes defensed, and one interception. In 2009, most of Barrett’s time came on special teams.

But before the 2010 season began, Barrett found out he would need shoulder surgery. The Broncos planned to put him on injured reserve, but he had to clear waivers first. The Patriots swooped in and claimed him and a couple of weeks later placed him on IR.

Throughout the year, Barrett said he stayed focused on his rehab.

“You never want to get too frustrated with it,’’ he said. “You want to control what you can control. Being healthy is a big part to being successful in this game. My approach to it is as long as I’m healthy, I’ll be productive. I’m just doing what I can do and more to get back on the field, [which is] where my focus was at that time.’’

Barrett said he did his best to learn what he could in meetings and watching film with his teammates.

“It was a long year, for sure,’’ he said. “It’s definitely the toughest situation I’ve been in, just not being in the groove and not being able to be on the field. The rehab and stuff like that is something you grind through.’’

This season, Barrett remained on the sideline until he was cleared to make his Patriots debut in the final preseason game against the Giants. He started beside Chung and picked up four tackles.

“The Xs and Os are one thing, but getting out on the field is a way different learning process,’’ he said. “You can try and do as much as you want in the classroom but really where you gain and where strides are made is on the field.’’

Barrett said he is comfortable anywhere on the field. After waiting so long to see action, he said he just wants to play and hopefully his performance will speak for itself.

“It’s more of a team concept,’’ he said. “I look at it as whatever I can do to help the team win . . . instead of having to prove anything.’’

Monique Walker can be reached at mwalker@globe.com.