Denver Broncos quarterback Peyton Manning is scheduled to announce his retirement from the NFL on Monday. Coaches, players, football executives and fans all came out Sunday to send their thanks to one of the greatest to ever play the sport, and the amount of respect number 18 received on the day he informed the team just shows the significance of impact he had on the league.

Manning is a surefire Hall of Famer, as his numbers put him in a class of his own. With NFL records that include the most single-season passing yards (5,477) and touchdowns (55), and career-records for most passing yards (71,490) and touchdowns (539). Manning became the only starting quarterback to win two Super Bowls with two different teams, and the Broncos' Super Bowl 50 victory gave him an NFL-record 200 wins throughout his career.

Manning will clearly frontline the 2021 Pro Football Hall of Fame class, but it's shaping up to feature at least a few first ballot Hall of Famers. Oakland Raiders and Green Bay Packers former free safety Charles Woodson is also expected to be first ballot Hall of Famer in 2021, as he announced his retirement prior to the end of the 2015 regular season.

Woodson's numbers speak for themselves as he is a nine time Pro Bowler, a Super Bowl champion and former defensive Player of the Year. Both Woodson and Manning spent 18 seasons in the league together, as they were both drafted in the first round of the 1998 NFL Draft, and it seems only fitting the two will share the stage in Canton.

Woodson recorded 1,204 combined tackles, 65 interceptions, 20 sacks, forced 33 fumbles, and scored 11 touchdowns during his career, and is considered one of the best to ever play the position. He and Manning are almost guaranteed to be voted into the 2021 class, but there are other potential first ballot Hall of Famers that could get the vote, as the NFL has lost some significant stars following the 2015 season.

Detroit Lions wide receiver Calvin Johnson has not made an official decision on his retirement, but reports came out in January stating that the Lions receiver had planned to hang it up after the 2015 season. Johnson could join the all-star cast in Canton in 2021, although he is not a shoe-in.

Johnson is currently 27th on the all-time career receivers list with 11,619 yards and holds the single-season receiving record for 1,964 yards, set in 2012. On the other side of the ball, pass rusher Jared Allen will be eligible for the 2021 Hall of Fame class, and his 136 career sacks currently has him on the top 10 list of all-time sack leaders.

Allen's personality and his ability to get after opposing quarterbacks could make a strong case for a first-ballot entry, and it wouldn't be shocking if he joined both Manning and Woodson in Canton. While Allen has a strong case to make the Hall of Fame, Marshawn Lynch will likely be the biggest question mark out of the stars eligible in 2021.

Lynch's agent has already confirmed his retirement, and the bruising running back's numbers are quite similar to Hall of Fame running back Earl Campbell. Lynch's Super Bowl championship is a huge plus when reviewing his résumé, and while he may not be a first-ballot Hall of Famer in 2021, Beast Mode will likely get in.

The Pro Football Hall of Fame class of 2021 should be a star-studded event with Manning and Woodson headlining. It's unknown who else will join those two in Canton, but it will likely prove to be one of the all-time greatest classes selected.