Celtic's inclusion in Friday's Europa League draw will be ignominious after they passed up a second chance at the Champions League by losing 1-0 to Maribor at Parkhead on Tuesday night.
The Hoops were beaten 6-1 on aggregate by Legia Warsaw in the third qualifier but were reinstated after the Polish club were effectively thrown out by UEFA for fielding a player who should have been suspended in the second leg at Murrayfield.
The Scottish champions were confident of reaching the group stages of the tournament for the third successive season after a 1-1 draw in Slovenia last week but Maribor skipper Tavares grabbed the crucial goal in the 75th minute to take the visitors through 2-1 on aggregate.
Celtic were booed off at the end of the game with some angry supporters gathering outside the main door to protest.
Those fans are unlikely to take any succour from the assessment of boss Ronny Deila, who admitted the Europa League was his side's level at the moment
The Norwegian said: "At the end, there is only one thing to say, we haven't been good enough and we haven't deserved to go to the Champions League.
"There is no excuse. We are not good enough. Now it is the Europa League and we will do everything we can to achieve things in that competition.
"That is our level now. We didn't lose because of the defending, we lost because we didn't create anything.
"We have to have more tempo and movement in our play, that is the job and it has to start now."
"We have to have more tempo and movement in our play, that is the job and it has to start now" - Ronny Deila
Deila, who is set to sign Ruban Kazan winger Wakaso Mubarak with discussion ongoing with Sporting Gijon's Serbian striker Stefan Scepovic, told angry fans that he will "work hard every day so we will be in a better situation next year".
He said: "We have to be honest. We haven't been good enough and that is the truth.
"I thought we had a good enough team to go through but we didn't do it."