Ange Postecoglou vowed to hammer home the need for new players after Celtic's latest dismal exit from the Champions League.
The Parkhead club suffered defeat in the qualifiers for the fourth straight year after an extra-time defeat to Danish champions FC Midtjylland.
A stunning strike from captain Callum McGregor looked set to tee up a clash with PSV in the third qualifying round.
Celtic boss Ange Postecoglou has vowed to hammer home the need for new players
Forced to field a second string defence after failure to land a raft of new faces, however, Posecoglou's side missed chances to kill the game before Awel Mabil levelled and substitute Raphael Onyedika claimed the winner early in extra-time.
Needing to win a treacherous clash with Czech side Jablonec to secure Europa League football until Christmas, the Australian took responsibility for failing outline the urgency of the situation to a Parkhead board facing the wrath of supporters.
'I think it's my responsibility,' he said. 'I'm the person who has been put in charge.
'We haven't got players in. Obviously I haven't done a good enough job convincing people we need to bring people in.
'I'm not going to shy away from it. I don't say that because I'm some kind of martyr.
'I just think that's my responsibility. That's why I was brought in.
Celtic are out of the Champions League after being beaten 2-1 by FC Midtylland in extra-time
'I've tried to be as forceful as I can about what we need to bring in. The challenges we've had are well chronicled, but irrespective of the result, we had a really young squad out there with young players on the bench, that's not the situation we need to be in.'
Swedish central defender Carl Starfelt will be free of covid quarantine restrictions in time for the SPFL opener at Hearts on Saturday evening. Japanese strike Kyogo Furuhashi is also close to a debut with Royal Antwerp right-back Aurelio Buta close and major shareholder Dermot Desmond spearheading a move for former England keeper Joe Hart.
Despite axeing Vasilis Barkas for keeper Scott Bain, Postecoglou could do little to change an inexperienced backline featuring Anthony Ralston, Stephen Welsh, Dane Murray and Greg Taylor.
Reiterating the need for more urgency in the transfer market he added: 'Maybe I wasn't clear enough, I don't know. I think I've been pretty consistent in saying we need more players in.
Awer Mabil pulled the home side level when he headed home Sisto's looping cross
'The club is working hard to get players in.
'We talk endlessly about the challenges
