Leggett fu scelto nel corso del primo giro (13º assoluto) del Draft NFL 1957 dai Chicago Bears[1] rimanendovi per undici stagioni (1957–1968). Giocò come defensive tackle e come defensive en, facendo parte della celebre difesa nota come "Monsters of the Midway" che guidò i Bears alla vittoria del campionato NFL del 1963. Fu scambiato con i Los Angeles Rams nel 1966, dove giocò dieci partite nella difesa chiamata "Fearsome Foursome". Nelle ultime due annate in carriera fece parte dei neonati New Orleans Saints, disputando 20 partite.
9 Bill Wade • 10 Rudy Bukich • 17 Richie Petitbon • 22 Billy Martin • 23 Dave Whitsell • 24 Rosey Taylor • 25 J.C. Caroline • 26 Bennie McRae • 28 Willie Galimore • 29 Ronnie Bull • 31 Joe Fortunato • 33 Larry Morris • 34 Joe Marconi • 35 Rick Casares • 43 Larry Glueck • 46 Angelo Coia • 47 Johnny Morris • 49 Charlie Bivins • 50 Mike Pyle • 60 Roger Davis • 61 Bill George • 63 Bob Wetoska • 65 Tom Bettis • 67 Ted Karras • 70 Herman Lee • 71 Earl Leggett • 72 Jim Cadile • 73 Steve Barnett • 74 Bob Kilcullen • 75 Fred Williams • 76 John Johnson • 78 Stan Jones • 80 Bob Jencks • 81 Doug Atkins • 83 Roger LeClerc • 84 Bo Farrington • 87 Ed O'Bradovich • 88 Bobby Joe Green • 89 Mike Ditka Capo-allenatore:George Halas • Staff:George Allen • Jim Dooley • Phil Handler • Luke Johnsos • Sid Luckman • Chuck Mather • Joe Stydahar
6 Marc Wilson · 7 Dan Pastorini · 8 Ray Guy · 10 Chris Bahr · 16 Jim Plunkett (MVP) · 20 I. M. Hipp · 21 Cliff Branch · 22 Arthur Whittington · 23 Odis McKinney · 26 Keith Moody · 30 Mark van Eeghen · 31 DDerrick Jensen · 33 Kenny King · 35 Dwayne O'Steen · 36 Mike Davis · 37 Lester Hayes · 42 Monte Jackson · 43 Ira Matthews · 44 Burgess Owens · 45 Mike Spivey · 46 Todd Christensen · 50 Dave Dalby · 51 Bob Nelson · 52 Mario Celotto · 52 Greg Westbrooks · 53 Rod Martin · 55 Matt Millen · 56 Jeff Barnes · 57 Randy McClanahan · 60 Alva Liles · 62 Reggie Kinlaw · 63 Gene Upshaw · 65 Mickey Marvin · 66 Steve Sylvester · 70 Henry Lawrence · 71 Lindsey Mason · 72 John Matuszak · 73 Dave Browning · 74 Dave Pear · 77 Joe Campbell · 78 Art Shell · 79 Bruce Davis · 81 Morris Bradshaw · 82 Dwight Harrison · 83 Ted Hendricks · 84 Derrick Ramsey · 85 Bob Chandler · 86 Cedrick Hardman · 88 Raymond Chester · 89 Rich Martini · 90 Willie Jones
Staff:: Sam Boghosian ·Willie Brown · Lew Erber · Chet Franklin ·Earl Leggett · Joe Madro · Bob Mischak · Steve Ortmayer · Charlie Sumner · Ray Willsey
6 Marc Wilson • 8 Ray Guy • 10 Chris Bahr • 11 David Humm • 16 Jim Plunkett • 20 Ted Watts • 21 Cliff Branch • 22 Mike Haynes • 23 Odis McKinney • 25 Irvin Phillips • 26 Vann McElroy • 27 Frank Hawkins • 28 Cleo Montgomery • 31 Derrick Jensen • 32 Marcus Allen(MVP) • 33 Kenny King • 34 Greg Pruitt • 36 Mike Davis • 37 Lester Hayes • 38 Chester Willis • 40 Rick Berns • 45 James Davis • 46 Todd Christensen • 47 Don Bessillieu • 48 Kenny Hill • 50 Dave Dalby • 51 Bob Nelson • 52 Jim Romano • 53 Rod Martin • 54 Darryl Byrd • 55 Matt Millen • 56 Jeff Barnes • 57 Tony Caldwell • 58 Jack Squirek • 61 Dave Stalls • 62 Reggie Kinlaw • 64 Shelby Jordan • 65 Mickey Marvin • 66 Steve Sylvester • 68 Johnny Robinson • 70 Henry Lawrence • 71 Bill Pickel • 72 Don Mosebar • 73 Charley Hannah • 74 Archie Reese • 75 Howie Long • 76 Ed Muransky • 77 Lyle Alzado • 79 Bruce Davis • 80 Malcolm Barnwell • 82 Calvin Muhammad • 83 Ted Hendricks • 84 Derrick Ramsey • 85 Dokie Williams • 87 Don Hasselbeck • 93 Greg Townsend
Staff:: Sam Boghosian • Willie Brown • Chet Franklin • Larry Kennan • Earl Leggett • Bob Mischak • Steve Ortmayer • Terry Robiskie • Art Shell • Charlie Sumner • Tom Walsh • Ray Willsey