Deila will leave Premiership champions Celtic after Sunday's match against Motherwell.
The Norwegian led the club to two titles and a League Cup win, but they were unable to reach the Champions League group stage this term and last.
"We did not play as well as was needed," said Sweden player Lustig.
"Of course Celtic always want to be in the Champions League, but at the same time, he is not to blame. The players are the ones out there.
"When we went out of the Champions League, we should have been the better team, but we were not at that standard."
Lustig feels it would be "a little bit harsh" to regard Deila's reign as a failure and said: "Hopefully the manager gets a good reception on Sunday.
"He's been here for two years now and obviously we wanted something more, but he has brought titles to the club and I think he's going to get a good send-off.
"We want to have a good win for the manager and make sure the last game is memorable."
Deila announced after a Scottish Cup semi-final defeat on penalties to Rangers that he would be moving on at the end of the season.
He will leave behind a large squad, of which Lustig said: "There is a lot of players in the same positions and that's maybe one of the weaknesses that we have.
"We don't have 11 to 15 players who are always in the first team - there have been a lot of changes between games.
"Of course everyone wants to play, but when you try to keep everyone satisfied, it ends up them maybe starting one game but then the next they are not in the squad.
"Or, from not being in the squad one week, you start the next game.
"As a player, you want to know if you're a first-team player or if your role is to come on for the last 20 minutes.
"So maybe there has been a little bit too much changing about.
"We will see what the new manager wants to do with the club. Maybe some will have to go, maybe he will bring in some new players as well."
Celtic defender Mikael Lustig insists Ronny Deila is "not to blame" for the club missing out on Champions League football under the manager's tenure.