Obviously, expecting a UDFA to become a Hall of Famer is a little much; frankly, so is expecting Super Bowl heroics. Nevertheless, that opportunity exists for those who weren't drafted over the weekend but still have signed with NFL teams.
The 15 Hall of Famers truly made their opportunities count. The 15: cornerback Willie Brown, cornerback Jack Butler, center Frank Gatski, kicker/offensive tackle Lou Groza, cornerback Dick "Night Train" Lane, center Jim Langer, guard Larry Little, quarterback Warren Moon, running back Marion Motley, running back Joe Perry, defensive tackle John Randle, cornerback Emmitt Thomas, defensive back Emlen Tunnell, nose tackle Bill Willis and cornerback Willie Wood.
Butler wasn't the only one-time UDFA to make a mark in the Super Bowl. While he wasn't a starter for the Patriots, New England did start five players in the Super Bowl who began their careers as free agents: punter Ryan Allen, cornerback Kyle Arrington, cornerback Brandon Browner and guards Dan Connolly and Ryan Wendell. The Seahawks started seven: wide receiver Doug Baldwin, defensive end Michael Bennett, kicker Steven Hauschka, wide receivers Jermaine Kearse, wide receiver Ricardo Lockette, defensive tackle Tony McDaniel and punter Jon Ryan.
And here's a look at some prominent current players who began their careers as undrafted free agents.
» San Diego Chargers TE Antonio Gates: He played college basketball at Kent State, and the Chargers thought he had NFL potential when they signed him in 2003. That was a nice move by the Chargers. He is a three-time All-Pro selection and an eight-time Pro Bowler. He has 788 career receptions and 10,014 receiving yards. Gates also has 99 career TD receptions, the most among active players and a figure that ranks ninth in NFL history. He had 12 TD catches in 2014, the second-highest single-season figure in his career.
» Miami Dolphins CB Brent Grimes: He played collegiately at Division II Shippensburg (Pa.). Grimes signed in 2006 with the Atlanta Falcons but was cut during training camp; he later was re-signed by the Falcons and played in NFL Europe in 2007. He made the Falcons' roster that fall and has been in the NFL since. Grimes made one Pro Bowl appearance with the Falcons, and has been to each of the past two as a member of the Dolphins. He has 22 career interceptions.
» Dallas Cowboys QB Tony Romo: He played collegiately at FCS member Eastern Illinois. He signed with the Cowboys in 2003 and remains with the team. He is a four-time Pro Bowler who holds the Cowboys' franchise record for TD passes with 242. He is 75-48 as a starter in his NFL career. The Cowboys were one of three teams in 2014 whose main starting quarterback began his career as a free agent; the others were the Cleveland Browns (Brian Hoyer) and St. Louis Rams (both Austin Davis and Shaun Hill were UDFAs and each started eight games last season).
» Miami Dolphins DE Cameron Wake: He played college ball at Penn State, as a linebacker named Derek Wake (his full name is Derek Cameron Wake). He signed with the New York Giants in 2005, but they cut him and he didn't play pro football until 2007 -- in the CFL, as Cameron Wake. Wake signed with Miami in 2009 and has been one of the Dolphins' best players ever since. He has been an All-Pro and also is a four-time Pro Bowler. He has had three seasons with at least 11.5 sacks, including 2014.
Among players of recent vintage who began as undrafted free agents were linebacker London Fletcher, running back Priest Holmes, center Jeff Saturday, wide receiver Rod Smith, quarterback Kurt Warner and wide receiver Wes Welker.