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High expectations await Rob Gronkowski as the former All-Pro tight end came out of retirement after one year to join the Tampa Bay Buccaneers -- and reunite with good friend Tom Brady. Gronkowski already has his Hall of Fame resume sealed, but he can add to his legacy as one of the best tight ends to ever play the game with a strong finish in Tampa. 

Gronkowski isn't the first high-profile NFL player to be lured out of retirement, and he likely won't be the last. Former NFL greats who returned to the game after officially retiring have typically performed at a high level, even in their mid-to-late 30s. Gronkowski is just 31 years old and still in his prime, so a good season or two may be ahead if he can stay healthy. 

These 10 NFL greats didn't need to return to football, but each had reasons to return and played at a high level in their second NFL life. Here are the 10 best NFL returns by players who had retired from the league: 

10. Reggie White

White shockingly returned to the NFL after retiring as a First Team All-Pro and finishing with 16 sacks with the Green Bay Packers in 1998 -- at 36 years old. The Carolina Panthers were looking to bolster their pass rush and lured White out of retirement in 2000, signing him to a five-year deal. 

White finished with a career-low 5.5 sacks, even though he started all 16 games at 38 years old. Not bad considering he signed in late July, when Panthers training camp was set to begin. He actually finished second on the team in sacks. 

White retired for good after the season as the NFL's all-time sacks leader with 198 (which Bruce Smith surpassed in 2003).

9. Ricky Williams

Shocking the NFL by retiring in his prime, Williams had tested positive for marijuana for a second time and was facing a four-game suspension. Using the time to "find himself," Williams studied Ayurveda, an ancient Indian system of holistic medicine, for a year before deciding to return. 

Williams started just three games in his first season back in 2005 with the Dolphins, rushing for 743 yards and six touchdowns in 12 games. He failed a drug test for a fourth time, and was suspended for the entire 2006 season -- playing for the CFL's Toronto Argonauts to stay in football shape. 

Williams rushed for 1,121 yards and 11 touchdowns in 2009 at the age of 32 (despite only starting seven games). After a 2007 season which he had to apply for reinstatement to the league, Williams didn't miss a game in the last four years of his career. 

He rushed for 3,655 yards and 25 touchdowns in the six seasons following his retirement. Williams wasn't the same player that took over the league in his first five seasons. 

8. James Harrison

Harrison initially retired with the Pittsburgh Steelers at 36 years old in 2014, but wasn't away from the NFL for long. Thanks to injuries piling up on the Steelers defense, Harrison was lured out of retirement weeks later. He started just four games, but finished with 5.5 sacks and 14 quarterback hits in 11 games.

Harrison never made a Pro Bowl in the four years after his return, even though he was the emotional leader on the Steelers defense. He recorded 15.5 sacks and 38 quarterback hits with two interceptions in a part-time role with Pittsburgh the first three seasons back, all in his late 30s. 

The Steelers played Harrison just 29 snaps in the first 12 games of the 2017 season, leading to his release in December of that year. The 39-year-old Harrison signed a contract with the Steelers arch-rival, the New England Patriots, days later and had two sacks in his first game with the team, a Week 17 win over the New York Jets.

Harrison started Super Bowl LII and played 91% of the snaps, finishing with two quarterback hits against the Philadelphia Eagles. He retired after the 2017 season, recording 17.5 sacks and 42 quarterback hits since returning at 36 years old. 

7. Deion Sanders

Hard to believe Sanders played at a high level at 37 years old, missing three seasons after retiring from the NFL in 2000. Sanders still had an itch to play and something to prove. Sanders actually was claimed off waivers by the San Diego Chargers in 2002 when Washington released him from the reserve/retired list, but it was too late for him to be activated so he never played a game for the franchise. 

Ray Lewis helped lure Sanders out of retirement in 2004 when he signed with the Baltimore Ravens, playing the slot after a decade as one of the best outside cornerbacks in the game. Sanders played in just nine games his first season back, but finished with three interceptions and had five passes defensed. He also returned an interception 48 yards for a touchdown in Week 7 against the Buffalo Bills, tying Ken Houston and Aeneas Williams for second place in interception returns for touchdowns in league history. 

Sanders played two years in Baltimore, finishing with five interceptions and 10 passes defensed in 25 games, retiring for good at 38. There aren't many cornerbacks who played well in their late 30s, but Sanders was one of them. 

6. Randall Cunningham

Hard to make a top 10 list without mentioning Cunningham's massive return to the NFL. After the Philadelphia Eagles released Cunningham and the St. Louis Rams failed to sign him, Cunningham walked away from the game at 33. 

Cunningham, who was a studio analyst for TNT and ran a granite business, signed with the Minnesota Vikings in 1997 as Dennis Green needed a backup quarterback. The former Bert Bell award winner had plenty of game left in him. Cunningham earned the starting job in Week 15 of the 1997 season and led the Vikings to a thrilling 23-22 overtime win over the New York Giants in the NFC Wild Card round, conducting two late scoring drives in the win. 

The 1998 season was Cunningham's best in the NFL, as he threw for 3,704 yards and 34 touchdowns to just 10 interceptions to lead the Vikings to a 15-1 record. Cunningham threw four touchdown passes in four separate games and led the NFL with a 106.0 passer rating, earning First Team All-Pro honors at the age of 35. He threw for 505 yards and five touchdowns in two playoff games, but the Vikings were shocked in overtime by the Atlanta Falcons in the NFC Championship Game, thanks to a missed 38-yard field goal by Gary Anderson -- who hadn't missed a kick all year.

Cunningham never recaptured that 1998 magic and lost his starting job in 1999, but played three more years as a backup quarterback. He signed a one-day contract to retire with the Eagles in 2002. Cunningham threw for 7,102 yards and 57 touchdowns to 29 interceptions following his return. 

5. Ed "Too Tall" Jones

Ed "Too Tall" Jones retired from the NFL at 28 after the 1978 season to pursue a boxing career. He actually went unbeaten in his six fights, but wasn't considered a true heavyweight contender. Jones returned to the Dallas Cowboys in 1980 with his best years ahead of him. 

Boxing made Jones a better football player, as the Cowboys legend made three Pro Bowls and was a First Team All-Pro selection once in the 10 seasons after his return. Sacks weren't an official stat until 1982, but Jones recorded 57.5 of them in the eight seasons they were official -- all after the age of 31. Jones missed just one game since returning to football and finished with 13 sacks in 1985 and 10 sacks in 1987 (at the age of 36). 

Somehow Jones isn't in the Cowboys "Ring of Honor" nor the Hall of Fame. He should be in both. 

4. Bronko Nagurski 

Nagurski took five seasons off before returning to the game in 1943, at the age of 35. The Bears were short of football players due to World War II, so Nagurski decided to come back as a tackle (he played fullback in his first eight seasons with Chicago). 

The Bears were trailing in a must-win game late in the season against the Chicago Cardinals, so they moved Nagurski back to fullback. Nagurski scored a touchdown to put the Bears within one score in the fourth quarter, as Chicago scored 21 unanswered points in the final quarter to send the Bears to the NFL Championship Game. 

Nagurski scored on a 3-yard run to give Chicago the lead for good in the title game, finishing with 11 carries for 34 yards and a score in a 41-21 victory. Nagurski went out on top after being away from the game for half a decade, one of the best returns in league history. 

3. Brett Favre

Favre actually retired twice, in 2008 with the Green Bay Packers and in 2009 with the New York Jets -- two of the weirdest sagas in NFL history. 

His decision to retire the first time came after Favre made a Pro Bowl at the age of 38 and he led the Green Bay Packers to the NFC Championship Game in that same season (2007). Shortly after announcing his retirement, Favre decided to return that summer. 

The Packers moved on from Favre and traded him to the New York Jets, where he led the league with 22 interceptions, but made the Pro Bowl. Favre completed 65.7% of his passes and threw for 3,472 yards and 22 touchdowns as the Jets collapsed from an 8-3 start to finish 9-7 and miss the playoffs. Favre played with a torn biceps tendon in his right shoulder the final month of that season. 

Shortly after the Jets' season ended, Favre retired again, only to come back and quarterback the Minnesota Vikings in August of 2009. He had arguably the best season of his career at age 40, completing 68.4% of his passes while throwing for 4,202 yards and 33 touchdowns to just seven interceptions (107.2 passer rating). 

The Vikings reached the NFC Championship Game as Favre took the eventual Super Bowl champion New Orleans Saints to overtime. Favre played one more season in Minnesota before retiring for good at age 41. He started 321 straight games at quarterback (regular season and postseason) and did not miss a game until his final season. 

Favre played his best football into his 40s with a shortened offseason, adding to his legendary career. 

2. John Riggins

Whether Riggins actually retired from the NFL is up for debate, but the Washington Redskins actually did place him on the retired list in 1980. Riggins wanted to renegotiate his $300,000-per-year deal with the Redskins, but the team refused. Riggins left camp that season and the team placed him on the camp-retired list, preventing him from going to another organization.

New Redskins head coach Joe Gibbs wanted Riggins back and gave him a peace offering. Riggins asked for a no-trade clause in his contract, and the Redskins obliged. 

Riggins returned at 32 years old, and he was dominant into his mid 30s. Riggins rushed for 4,530 yards and 62 touchdowns in five seasons, having two 1,000-yard seasons and leading the league in touchdowns twice (including a staggering 24 in 1983 at the age of 34). His finest performance came in Super Bowl XVII, rushing 38 times for 166 yards and a touchdown -- a 43-yard run on fourth-and-1 that gave the Redskins the lead for good and became one of the most iconic plays in NFL history. 

Those final five years made Riggins a Hall of Famer, capped with a Super Bowl MVP award and a single-season touchdown record that stood for 12 years. 

1. Otto Graham 

Graham retired from the NFL after the 1954 season, after the Cleveland Browns crushed the Detroit Lions 56-10 in the NFL Championship Game. Head coach Paul Brown begged Graham to return after his replacement quarterbacks struggled in the 1955 preseason. 

Graham returned and had one of his finest seasons at 33 years old, leading the league in completion percentage (53.1), yards per attempt (9.3) and passer rating (94.0), throwing for 1,721 yards and 15 touchdowns as the Browns returned to the NFL Championship Game. He also was the UPI MVP and a First Team All-Pro. 

Graham threw for two touchdowns and rushed for two touchdowns as the Browns crushed the Los Angeles Rams 38-14 in the title game. He walked off the field with his seventh pro football championship in his 10 seasons (three in NFL, four in All-American Football Conference) -- making a championship game in all 10 seasons he played professional football. 

Not only did Graham leave a champion, but he had the best post-retirement comeback of all time.