The Hoops boss said that he was "irritated" by his team's attacking display, but applauded their efforts to secure the winner after the Buddies had drawn level.
"I feel a little bit irritated that we didn't play well offensively and have more chances," Sky Sports News quotes Deila as saying.
"It was not the best performance we ever had. It was a tough game and we looked a little bit tired. We were too slow on the ball and we didn't create as many chances as we needed.
"But I know it is tough to play three games in a week and win. Some days football is just hard work. It was a positive thing that we came back after 1-1 to win the game and didn't give them many chances."
The result leaves Celtic in fourth place in the Scottish Premiership table.