Halfback Williams hurt his hamstring in Saturday's dominant defeat of the Western Force and on Monday was ruled out of the nine-game tour.
Scottish No.9 Ben White has been drafted into the squad and will join the side in Brisbane, where gloomy weather welcomed them ahead of Wednesday's Suncorp Stadium clash.
Coach Andy Farrell has named a strong side to face Les Kiss's men, with English lock Itoje joined in the second-row by countryman Ollie Chessum.
Farrell has made 14 changes in total, with Irish fullback Hugo Keenan and halfback Jamison Gibson-Park both earning Lions debuts.
Finn Russell retains the No.10 after a sizzling showing in Perth while Auckland-born Irish centre Bundee Aki will make his first tour appearance.
Firebrand English prop Ellis Genge has been named on the bench while No.8 Jack Conan gets his chance in a new-look backrow.
The Reds will name their team, expected to be stacked with Wallabies hopefuls, later on Monday.
The Lions will play the NSW Waratahs in Sydney on Saturday and the first Test is in Brisbane on July 19.
LIONS: Andrew Porter, Ronan Kelleher, Will Stuart, Maro Itoje, Ollie Chessum, Tom Curry, Jac Morgan, Jack Conan, Jamison Gibson-Park, Finn Russell, Duhan van der Merwe, Bundee Aki, Huw Jones, Tommy Freeman, Hugo Keenan. Bench: Luke Cowan-Dickie, Ellis Genge, Finlay Bealham, James Ryan, Ben Earl, Alex Mitchell, Fin Smith, Garry Ringrose.
6°C