The Stromsgodset boss flew into Glasgow on Thursday night after he became the surprise candidate to replace Lennon, who left the Parkhead club two weeks ago after four years in charge.
Lennon's departure came after assistant Mjallby announced in April that he would be leaving at the end of the season to seek new challenges.
Deila could be confirmed as Hoops boss on Friday, with reports claiming former Celtic and Scotland midfielder John Collins is in the frame for the assistant's role, but Lennon claimed it the 38-year-old Norwegian could have been involved in a different set-up at the Glasgow club .
"He was going to be brought in as number two when Johan Mjallby left," the former Celtic skipper was quoted as saying in the Irish Independent.
"He came highly recommended, he's highly thought of.
"I don't know if it's confirmed with Celtic yet, but I know from contacts in the game that he is well respected as a coach.
"We recruited Stefan Johansen from Stromsgodset, so we were aware of his work. It'll be interesting to see if Ronny gets the job."
Lennon was "surprised and a little bit disappointed" that former Celtic and Manchester United midfielder Roy Keane had asked not to be considered for the Parkhead post.
The Irishman opted to stay on as Republic of Ireland assistant to Martin O'Neill, although he has been linked with the number two job at Aston Villa under Paul Lambert.
"I think he's ready for it," said the Northern Irishman. "He's had, what, three years since he was out of the game as a manager and he's been watching a lot of games, he's been at Champions League games, and he's got vast experience.
"He fits the identikit of a Celtic manager. I can totally understand his situation, that it's a personal decision, but I was hoping he would take it.
"He would have given the club a big lift."