When the NFL free-agency period begins Thursday, there will be a feeding frenzy for the top-ranked players. They will get multiple mega-deal offers, and they will have their pick of them.

But there’s another level of free agent that teams should pay attention to as they line up their potential signings.

I’ve identified five guys who are under the radar some when it comes to this free-agency class, but all five can help improve a team.

All five, by the way, fall into the all-important target age of 26 or 27 for free-agent signings.

These players might not be gone on the first few days, although a few have a chance, but keep an eye on where they end up. I think they will be factors in 2017, wherever they play.

He started seven games last season for the Packers, and did a nice job in place of Corey Linsley. He did injure his knee, and had it scoped after the season, but he is expected to be ready for the 2017 season.

Tretter is 26 and has 10 starts in his four seasons with the Packers, not counting playoffs. They all came at center in the regular season, but he started at left tackle in the 2015 playoffs against the Redskins and has played guard as well.

That versatility will help drive up his market, but he is considered by most to be a center, and a good one. He is smart, can make the calls, which is imperative in the Green Bay offense, and his is good in the run game and solid in pass protection.

He won’t overpower bigger nose tackles, but he makes up for it with his technique.

For a team looking for a quality starter, one with a lot good football in front of him, Tretter could be great value.

Tretter won’t overpower bigger nose tackles, but he makes up for it with his technique. USATSI

In 2015, Aiken caught 75 passes for 944 yards and four touchdowns. But with Steve Smith back healthy last year, Aiken didn’t play as much as his production fell to 28 catches and one touchdown.

The enticing thing is that he’s just 27 years old, which means he has some good football left. For a receiver-needy team, he could be a nice second or third option. He will never be the No. 1 guy, but could be a solid complementary player to a big-play threat on the other side.

Aiken bounced around the league, getting cut by three teams, before settling with the Ravens three years ago. In the past two seasons, he’s had nine games where he averaged 15 yards or more per catch and in six of those he had at least five catches.

That’s some playmaking ability, which is why he might be a guy who could be a steal for a team.

Aiken could be a nice second or third option for a team. USATSI

Simon’s 2016 season, his best in the league, was cut short by a chest injury that limited him to 11 games and five starts.

Even so, he had 3½ sacks and did a nice job as a starting outside linebacker the first five weeks.

Simon does a nice job playing the run and he is an effort player when it comes to rushing the passer. He isn’t a blow-by pass rusher, but he has 10 sacks the past three seasons. He doesn’t turn 27 until October, so he is in the prime of his career.

For a team looking for a 3-4 outside rusher -- maybe division-rival Indianapolis -- he would make a lot of sense.

Simon has 10 sacks the past three seasons. USATSI

If a team is looking for a hybrid player, a guy who can play corner, safety, slot, buck linebacker or anything in the secondary, Hyde is that guy. He has been a valuable part of the Packers secondary the past few seasons, but he is kind of a guy without a position.

Even so, he has great value in this era of the hybrid player. He played safety and corner last year and had three interceptions over the final four weeks, getting one in the playoffs against the Cowboys. He can also blitz from the slot and can play in the deep middle if need be.

The Packers got creative in the ways they used his skill set, which is what a new team would need to do. He isn’t going to line up and play corner outside, although I think he could be a starting safety for some teams.

The way the game is played now, hybrids have value. That’s why Green Bay might not be able to bring him back.

Hyde can play corner, safety, slot, buck linebacker or anything in the secondary. USATSI

He was the Raiders’ best inside down player last year, but he missed seven games with injuries. That’s a problem and it could drive his price down some.

McGee, who turned 27 in January, had 2½ sacks last season, but it was his run play inside that is his calling card. At 6-3, 310 pounds, he is a power player who can hold up at the point.

He made big strides last season from his first three in the league, which means he’s an ascending player. That matters. He has 18 starts in his four seasons for the Raiders. Teams looking for a good, young run player should pursue McGee.