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These three were added because they are all undrafted free agents with three different paths to their NFL careers.
With Warren Moon, after becoming undrafted, he played five seasons in the CFL.
His team would win an unprecedented five straight Grey Cups during his tenure.
After that, NFL teams started to bid for him and he was finally given an opportunity to play in the NFL.
Thus, he did not play his first game in the NFL until the age of 27 but would end up being one of the best quarterbacks of all-time.
Over the course of his career, he became a nine-time Pro Bowler and a three-time All Pro.
Moreover, he amassed 49,325 passing yards and 350 TDs. If the NFL combined his stats with the CFL, he would have gain over 70,000 passing yards for his career.
In fact, he is the only player in football history to be a part of both the Canadian Football HOF and the NFL Hall of Fame.
Adam Vinatieri played college ball with Division II South Dakota State. After he went undrafted in the NFL draft, he actually played a season in NFL Europe with the Amsterdam Admirals.
His team would lose in the World Bowl III, but he would be signed by the New England Patriots as a free agent in 1996.
The rest is history. He has played in five Super Bowls with the Colts and Patriots (sat out the sixth one with an injury), winning four of them and has been labeled as one of the "Greatest clutch kickers in NFL history!"
In addition, he was named to NFL's 2000s All-Decade Team.
Kurt Warner's story is truly remarkable. After being undrafted in the 1994 NFL draft, he was signed by Green Bay but released before the regular season started.
Therefore, he stocked shelves at a Hy-vee grocery store and became a graduate assistant at Northern Iowa. After that, he played in the AFL (Arena Football League for the 1996 and 1997 seasons and finished first team All-Arena both years.
After the 1997 season, he got a tryout with the Chicago Bears, but an injury to his throwing elbow prevented it from occurring.
Then, he signed with the St. Louis Rams for the 1998 season, and he actually was the third-string backup to Tony Banks and Steve Bono.
Finally, in 1999, the Rams signed Trent Green, but due to an injury, he became the starter and his career took off.
Similar to Moon, he didn't get to start a game until the age of 28, but he would become one of the most dominant quarterbacks of the 2000s.
He has played in three Super Bowls, winning only in his first appearance (1999).
Moreover, he has countless records that could be an article on its own.
However, the most remarkable tidbit is that he owns the first, second and third spots for most passing yards thrown in a Super Bowl.