The NFL announced Wednesday that linebackers would now be eligible to wear jersey numbers in the 40s going forward, marking a change in the jersey numbering system that was adopted by the league in 1973.
An amendment to the rule in 1984 allowed linebackers to also wear jersey numbers 90-99, but prior to Wednesday's announcement, numbers in the 40s were off limits.
The same jersey numbering system does not apply in college, so linebackers can wear numbers in the 40s while they play collegiately.
Khalil Mack was one of those linebackers, wearing 46 while he played at the University of Buffalo, but ultimately switching to 52 when the Raiders selected him No. 5 overall in the 2014 NFL Draft.
So, if he were so inclined, what would Mack have to do to change back to his college number?
According to the NFL, first he would have to talk to the Raiders about a new number, who would then reach out to the league to alert them that they support his number change.
Next, the league and Nike would determine the amount of inventory that they had in stock featuring his old number and Mack would be responsible for buying out that inventory before he could officially make the change back to 46.
If the former Buffalo Bull were to eventually return to his old number, he would join a lengthy group of Raiders linebackers who spent their time in Silver and Black wearing numbers in the 40s.
No. 41 Phil Villapiano –LB- 1971-79
Selected by the Raiders in the 2nd round of the 1971 NFL Draft, Villapiano played in 118 games with 117 starts. He recorded 11 interceptions for 160 yards and 1 TD and recovered 17 fumbles. He was a key member of several playoff teams including the Raiders Super Bowl XI championship team. He made the game-sealing interception in the Sea of Hands game against Miami in the 1974 playoffs.
No. 41 Eric "Crazy" Johnson –DB/LB-2000-03
Johnson played in 55 games with 2 starts and recorded 1 interception. The special teams ace returned a punt blocked by LB Tim Johnson for a touchdown in Super Bowl XXXVII.
No. 42 Bill Laskey –LB-1966-70
Laskey joined the Raiders after a year with Buffalo. He played in 53 games with 22 starts and recorded 4 interceptions for 66 yards and recovered 5 fumbles. He went on to play for the Colts and Broncos.
No. 45 Greg Slough-LB-1972
The Raiders selected Slough in the 6th round of the 1971 NFL Draft out of USC. He wore No. 58 in 1971 and No. 45 in 1972. In all, he played in 22 games and recovered one fumble.
No. 45 David Fulcher-LB-1993
Fulcher joined the Raiders after seven years with the Bengals and played in three games in 1993.
No. 46 Bill Enyart-LB-1971
After spending two seasons with the Buffalo Bills, Enyart played in one game for the Raiders in 1971.
No. 48 Charlie Rieves-LB-1963
Rieves wore No. 32 in 1962 and No. 48 in 1963. In all, he played in 23 games for the Raiders. He went on to play for the Houston Oilers from 1964-65.
No. 48 Bill Budness-LB-1964-70
The Raiders selected Budness in the 4th round of the 1964 AFL Draft out of Boston University. He played in 92 games and intercepted 3 passes for 29 yards.
No. 49 Jackie Simpson-LB-1962-63
Simpson joined the Raiders after a season with the Denver Broncos. He played in 30 games from 1962-64 and racked up five interceptions for 39 yards. Simpson also made 3 of 10 field goal attempts and 6 of 7 extra point attempts. He returned one kickoff for 11 yards. He wore No. 49 from 1962-63 and No. 50 in 1964.
No. 49 Carl Weathers-LB-1970-71
Renowned actor Carl Weathers of Rocky fame wore the Silver and Black before donning Apollo Creed's red, white and blue boxing trunks. He played in a total of eight regular season games before hanging up his cleats and pursuing a film career.