The Celtic manager admits the squad he inherited simply wasn't up to the task of qualifying this time round, as the 6-1 aggregate defeat by Legia Warsaw hammered home.
But, the quality is almost certain to be further reduced with Fraser Forster and Virgil van Dijk set to make a quick exit to England in moves which will bring in around £15million - money Deila hopes to be allowed to re-invest in the players he insists he needs to produce a team good enough to compete at the top level.
The Norwegian is quoted by one bookmaker as favourite to be first SPFL manager to lose his job. But Deila is ignoring such speculation and focusing only on rectifying what went wrong in the 4-1 defeat in Warsaw and again when Legia won 2-0 in the second leg at Murrayfield.
He knows that, short-term, he has to right the badly-listing ship in time to safely steer the club through the play-off round of the Europa League, the draw for which is tomorrow with the ties starting two weeks tonight.
But, the longer-term aim is to be better prepared for next season's Champions League, where he is determined to return the Parkhead club.
He said: "I came in here six weeks ago to do a job, and I've started to do that. But, right now, it is not good enough. We need to make the squad better, and we're working every day on getting new players.
"But, we also have to do the best with what is here. There's a lot of skill and quality, but they haven't shown it in the last two games. That's what I'm going to work for in the next games."
There will be no knee-jerk reaction, however. Deila - who admitted Legia were the better team - has already had the opportunity to bring in players, but refuses to sign players simply to increase numbers because he only wants men he knows can perform to the system he is introducing to the club.
He is in for the long haul and prepared to build the squad he believes is required to reach previous heights in Europe.
If he does lose key men such as Forster and Van Dijk, he said: "Then I will just have to build up a new team. For the past two years we have been in the Champions League.
"This year we were by far not good enough to go into the Champions League. That's our goal as a club, and we have to do everything to qualify next year.
"We need players with pace and ambition, and who are young because I want to be on top with a team here who can last for many years."