Pernell attended Pahokee High School, where he was teammates with Dwight Bentley and Janoris Jenkins.

He helped lead Pahokee to a 14–0 record that included a 25–11 win over John Brantley's Ocala Trinity Catholic for the 2006 FHSAA Class 2B State Championship.

He originally signed with the University of Southern Mississippi out of high school before going the community college route.

[4] During his career at ICC, he tallied 124 tackles (92 solo), 32.5 sacks, 73.5 TFL, 47 QB pressures, and 4 FFs in 18 games.

During his MSU career he started all 25 of the games in which he appeared and totaled 91 tackles (46 solo), 7 sacks, 22 TFL, 20 QB pressures, 2 FFs, and 4 pass breakups.

[10] McPhee collected 6.0 sacks as a rookie for the Ravens in 2011, plus 23 tackles and a forced fumble while playing in all 16 regular season games.

On January 12, 2013, in the AFC Divisional Playoff against the Denver Broncos, McPhee recorded a strip-sack on quarterback Peyton Manning.

On January 20, 2013, in the AFC Championship against the New England Patriots, McPhee tipped a pass from quarterback Tom Brady that led to an interception by Dannell Ellerbe with 6:49 remaining in regulation.

This led to the Ravens winning that game 28–13 and earning a trip to Super Bowl XLVII, where they would defeat the San Francisco 49ers by a score of 34–31.