Owen Hargreaves and Rio Ferdinand believe Chelsea need new signings in order to bolster the squad.
Frank Lamprad's side suffered a 3-0 Champions League loss to Bayern Munich on Tuesday night, as brace from Serge Gnabry and a late goal from Robert Lewandowski secured their side's win.
Speaking to BT Sport, former Manchester United and Bayern Munich star Hargreaves said:
"At least four or five [signings] – not just quantity but quality.
"Real quality players who can make the difference. Every Bayern Munich player made a difference today at some point in the game.
"Frank had too many players who haven’t played enough football – whether it’s [Ross] Barkley or [Olivier] Giroud."
Rio Ferdinand then added:
"He [Lampard] is going to have to implement his own philosophy.
"But he’s also going to have to dip into that transfer market and make some waves with the opportunity he has in the next window.
"Up front [is where he most needs to add] – Tammy Abraham does score but he’s young and needs someone to come and help with that responsibility."
Chelsea, currently fourth in the Premier League, are set to face Bournemouth on Saturday.