The American was in sensational form at the end of last season, scoring and assisting in a thrilling match at Anfield after the restart, but he picked up a hamstring injury in the FA Cup final against Arsenal.
Lampard had been optimistic about Pulisic’s recovery but he suffered a setback before the trip to face Brighton on Monday night and is still struggling.
Summer signings Ben Chilwell and Hakim Ziyech are also still recovering from their own injury problems, while Thiago Silva is lacking match fitness, though Timo Werner is fine.
‘Chilwell is not ready for the game, neither is Christian Pulisic,’ confirmed Lampard at his pre-match press conference on Friday.
‘We hope they will work well during the week.
‘Thiago has been training for the last three or four days, but Liverpool will come too soon for him.’
Chilwell arrived at Chelsea carrying an injury while Ziyech picked up a knock in the club’s only pre-season friendly against Brighton.
None of the quartet are expected to be risked if fit against Barnsley in the Carabao Cup next Wednesday, though they may target a return to action against West Brom at the Hawthorns on September 26.