Don't overlook restricted free agency during the NFL's busy offseason. 

A restricted free agent is a player with an expired contract who has played at least three seasons in the league and received a qualifying offer from his team. Typically, they're either formerly undrafted players or draft picks who were released and later signed by either another team or the one that first selected them.

Once a player's contract expires, his team can extend one of three qualifying offers: a first-round tender, a second-round tender or an original-round tender (the round in which the player was originally selected). After a team commits to one of those three options, all 31 other franchises are allowed to negotiate a contract with that player in free agency. If another squad agrees to a deal with the player, it must trade the pick corresponding with the type of tender to the previous team...but only if the original organization chooses not to match the offer. 

This year, a handful of names could garner significant interest on the restricted free-agent market. Let's take a look at the five who could cash in big this offseason. 

WR Robby Anderson, New York Jets

Arguably the best player in restricted free agency, wide receiver Robby Anderson should receive a substantial amount of interest this offseason. The New York Jets signed him as an undrafted free agent out of Temple in 2016, and he has impressed ever since.

This free-agency class is devoid of great talent at the position, and Anderson could be the best receiver on the market. In his last 23 games, the 6'3" wideout has tallied 92 receptions for 1,362 yards and 11 touchdowns. More impressively, he's done so while Bryce Petty, Josh McCown and Sam Darnold throw him the ball. 

Anderson is already a big-play threat, and he's shown an ability to keep improving. Assuming he can play with a more consistent and reliable quarterback, he could even make the Pro Bowl soon.

He received a second-round tender from the Jets, but a few organizations might still come after the 25-year-old receiver. A team searching for a proven commodity at the position could very well pay up for his services. 

LB Cory Littleton, Los Angeles Rams

Pro Bowlers don't often make it to restricted free agency, but linebacker Cory Littleton will be an exception.

The Los Angeles Rams signed Littleton as an undrafted free agent in 2016, and he has since started 21 games for the team, including all 16 during the 2018 campaign.

Last season, the third-year standout made his first Pro Bowl as he recorded 125 total tackles, 13 pass deflections and three interceptions. He was also named a second-team All-Pro linebacker at just 25 years old. While he still has some issues in the run game, Littleton has developed into one of the NFL's best cover linebackers. That alone should make him an attractive free agent this offseason.  

Teams that need linebacker help should inquire about the former Washington Husky, especially if the Rams only use a second-round tender on him. The 2019 NFL draft lacks depth at the position, and it's hard to imagine anyone landing a better linebacker after the first day. Expect Littleton to have a market this offseason.

RB Jalen Richard, Oakland Raiders

Running backs don't typically receive a lot of attention in free agency. Especially not restricted free agents at the position.

However, Jalen Richard of the Oakland Raiders may be one of the few exceptions. He isn't your typical running back, carrying the ball just 194 times for 1,025 yards in his three-year career. He's been successful with his opportunities (5.3 yards per carry), but that certainly isn't his strength. 

His game is instead built around his ability to make plays in the passing game.

In 2018, Richard set career highs in receptions (68) and receiving yards (607) as a featured piece of Jon Gruden's offense. He's a dynamic pass-catcher who has averaged 8.5 yards per reception in his career, even though most of his targets take place near the line of scrimmage. Per ESPN, 502 of his 607 yards came after the catch last season, which put him 134 ahead of Oakland's second-place finisher, Jared Cook. 

He also had 23 receptions that resulted in a first down—the fourth-most on the team, behind Cook (46), Jordy Nelson (36) and Seth Roberts (24).

If a playoff-caliber team is looking for a proven passing-down back without a lot of wear and tear, Richard would make sense. Expect him to receive interest in the restricted market this offseason, especially from pass-heavy teams.  

LB Patrick Onwuasor, Baltimore Ravens

Baltimore Ravens linebacker Patrick Onwuasor may be an underrated name in restricted free agency, but he'll generate interest all the same.

After going undrafted out of Portland State in 2016, Onwuasor joined Baltimore's 90-man roster that May. However, he didn't make the final roster and was released in September. He bounced on and off the team's practice squad before eventually finding a consistent role on the defense one year later.

Onwuasor is an undersized linebacker (6'0", 227 lbs) who started 25 games and appeared in all 32 contests over the previous two seasons. Last year, he recorded 59 total tackles, 12 quarterback hits, eight tackles for loss and two forced fumbles. The 26-year-old is an ascending player whose best football is still ahead of him. 

The Ravens are allowing Pro Bowl linebacker C.J. Mosley to test the open market but could lose another starting linebacker if they aren't careful. Onwuasor should draw some interest, despite Baltimore putting a second-round tender on him, per ESPN Ravens reporter Jamison Hensley.

WR Rashard Higgins, Cleveland Browns

Rashard Higgins is another receiver who could cash in big on the open market.

Originally a fifth-round pick by the Cleveland Browns in the 2016 NFL draft, he was cut before the start of the 2017 season. But he signed with the team's practice squad and was elevated back to the active roster later that year.

While Higgins has been a part-time player in Cleveland, he's also been effective and efficient. Per Pro Football Reference, he caught 74.2 percent of his targets during his last 16 games, tallying 670 yards on 42 catches. Earning 14.6 yards per receptions, he showed he can be a reliable target over the middle of the field and projects as a No. 2 or No. 3 wideout going forward.

As reported by NFL.com's Tom Pelissero, the Browns placed an original-round tender on Higgins, so another team could sign him and only have to surrender a fifth-round pick. If any squad is looking for a cheap way to improve its wide receiver corps without gambling on a rookie, he could be one of the more intriguing options in restricted free agency.