Aeneas Williams did not play competitive football during his first two years at Southern University. He only joined the team as a junior, but by his senior year, he led the nation in interceptions and quickly attracted the attention of the Phoenix Cardinals, who picked him in the third round of the 1991 NFL Draft. What began as a low-profile pick developed into an impressive fourteen-year career—marked by his exceptional coverage skills and legendary ball-hawking instincts—establishing him as one of the top boundary defenders of his time.

Williams relied not on sheer size to challenge wide receivers but on sharp route recognition and spatial advantage. He excelled at mirroring top wideouts closely, maintaining smooth footwork during his backpedal, and then using a powerful burst to intercept passes. His natural hands turned contested throws into turnovers, complemented by superb open-field tackling. His quick diagnostic skills kept him a constant scoring threat following turnovers, with an impressive 9 career interception return touchdowns—tying him for second in NFL history at retirement.

Williams's debut in the professional ranks in 1991 instantly transformed his scouting profile. He secured the starting right cornerback position right after training camp, delivering an exceptional rookie season by recording a league-high 6 interceptions, earning PFWA All-Rookie honors, and placing third in the AP NFL Defensive Rookie of the Year voting. When he moved to the left cornerback position under defensive coordinator Fritz Shurmur, his dominance over the boundary became even more evident. In 1994, Williams completely shut down opposing passing attacks, leading the NFL with a career-best 9 interceptions and earning his first Pro Bowl selection.

That exceptional campaign sparked a remarkable six-year period of dominance in the desert. From 1994 to 1999, Williams earned six straight Pro Bowl selections as the key defensive stalwart for the rebuilding Cardinals. His outstanding performance was clearly demonstrated in 1995 when he made 6 interceptions—returning two for touchdowns—earning his first first-team All-Pro honor. He maintained that elite coverage level in 1997, again intercepting 6 passes and earning his second consensus first-team All-Pro selection. Williams proved himself as the crucial game-changer during the 1998 postseason, intercepting two passes in a thrilling wild-card upset against the Dallas Cowboys, leading the franchise to its first playoff win in fifty years.

As the Cardinals embarked on a major rebuilding phase at the start of the 2000s, the experienced boundary cornerstone was traded to the St. Louis Rams in spring 2001. Williams smoothly brought his veteran leadership to the Rams' secondary, eventually transitioning to safety later on. He received two more Pro Bowl selections and a first-team All-Pro honor in St. Louis, playing a crucial role in leading the Rams to Super Bowl XXXVI. After retiring following the 2004 season, he totaled 55 career interceptions, of which 44 were while he played for the Cardinals.

Williams was named as a premier boundary selection to the NFL 1990s All-Decade Team, and his eternal connection to football immortality was finalized in 2014 when he was enshrined in the Pro Football Hall of Fame.  The Cardinals honored him six years earlier by selecting Williams for their Ring of Honor.