Paul Lambert believes former club Celtic are “nowhere near good enough” without further recruitment – but has guarded against “panic”.
Striker Camilo Duran is the sole summer arrival so far for the Scottish champions, while midfielder Alex Oxlade-Chamberlain has signed a new contract after a short-term deal last term.
But forward Kelechi Iheanacho and former left-back loanee Marcelo Saracchi, who had been linked with returns, will not be back in Glasgow this season.
Iheanacho has joined Bursaspor as a free agent, while Saracchi bade farewell to Celtic fans on social media and said he and his agent “did absolutely everything within our power to make a return to Glasgow happen”.
Furthermore, German centre-half Maik Nawrocki has been sold by the Scottish champions to Lens.
“The squad’s not strong enough,” Lambert told BBC Radio Scotland’s Sportsound.
“I’ve seen Celtic, they’re nowhere near good enough at this moment in time, nowhere near it. Everybody recognises it.
“They’ll compete, but I don’t think they’re strong enough to go and win it [the league] again at this moment in time. The problems were there last season, so they’re not going to change again this season.
“The squad was very, very limited on what it was last season. They won’t get away with that again – the manager knows it.”