The Hoops are still on a high following their remarkable 2-1 home win over Barcelona earlier in the month and take on Benfica at the Stadium of Light on Tuesday night knowing that a victory would ensure qualification through to the knockout stages of the competition with a game remaining. Indeed, a scoring draw would take Celtic through if Spartak Moscow fail to beat Group G leaders Barcelona in Russia. The former Celtic defender tried to put in context what it would mean for the Scottish champions to reach the last 16 of the competition for the first time since 2007/08.
"It would be a wonderful achievement for the players and the management," said Mjallby.
"Obviously we can't compete financially with the other three clubs in the group.
"So I think it speaks volumes for the players, how hungry they are and their desire to improve all the time.
"No one gave us a chance when the draw was made but we always believed in the players and maybe they did even better than we expected."
Hoops manager Neil Lennon, though, is guarding against the growing feeling that Celtic are all but assured of a place in the knockout stages. The former Celtic skipper is aware that Benfica will be going all out to get the win they need to retain their interest in the competition.
"We have done remarkably well to be in the position we are in on the back of beating Barcelona but that's gone now," said Lennon.
"We have two huge games left in the competition and this game is very important for both teams.
"This was always going to be a pivotal game for us, regardless of the Barcelona games.
"You are never relaxed whoever the opposition is, particularly at this level.
"The landscape of the group can change on one night. This will be as tough as Barcelona, if not tougher.
"We might get two bites of the cherry but we would like to do it at the first time of asking. But we will have to do very well."