The Norwegian made 10 switches from the midweek draw at Maribor in the Champions League play-off, with only captain Charlie Mulgrew retaining his place ahead of the return leg at Parkhead.
Inverness triumphed 1-0 at the Tulloch Caledonian Stadium thanks to Eoghan O'Connell's 65th-minute own goal.
Deila admitted the number of changes may have been too great, but felt the sacrifice would prove worthwhile if they beat Maribor on Tuesday.
"I learned a lot about the players that came in but maybe there were too many new players," he said.
"There were probably too many at the same time and we didn't get the performance we wanted. We now have to focus on Tuesday.
"I have to congratulate Inverness because they played well but we had the better chances in the first half.
"You will see on Tuesday if I regret making too many changes, but of course it will be worth it if we win."
The Bhoys had no new injuries coming out of the game and starting goalkeeper Craig Gordon was merely rested ahead of the Champions League encounter. Kris Commons is also expected to be involved.
Celtic hit the bar in the first half through Nir Biton, while Teemu Pukki had two efforts blocked by the feet of Dean Brill.
Greg Tansey came closest for the visitors early on but it was not until O'Connell's own goal that they breached the back line.
The win for Caley Thistle maintained their place at the top of the table and marked their first win over the champions in Inverness since May 2011.
Manager John Hughes hailed the victory as "different class".
"To beat Celtic and to keep a clean sheet is absolutely different class," he said.
"We rode our luck a bit in the first half and had Dean Brill to thank for a few saves. But to beat them you need that luck.
"I totally understand them making that many changes and, to be honest, I would have done the same in their position. They have a massive game on Tuesday.
"I wish them well, I do, because it's good for Scottish football.
"But we played some real good stuff, created a lot of chances and showed a desire to keep a clean sheet."