Dundee United manager Jackie McNamara repeated his belief that mounting a title challenge would be a tall order despite beating Celtic 2-1.
Goals from Nadir Ciftci and Stuart Armstrong took United to within four points of the reigning champions.
Aberdeen are level on points with McNamara's team, who have a superior goal difference.
"You've got to perform like that with a bit of luck week in, week out," McNamara explained.
"It's a big ask. Aberdeen will say the same. We can only do our best and see where we are at the end of the season.
"I'm delighted with the effort and commitment and I think the players gave everything they had. They were absolutely knackered at the end.
"We rode our luck. Celtic put us under a lot of pressure.
"At moments, we caused them problems and we got the goals. We had a bit of a nervy ending when [Leigh] Griffiths gets that goal.
"You need a little bit of luck when you're playing Celtic. You're competing against international players.
"We had five or six players out. We were up against it for their energy. I was worried about [Calum] Butcher, but he was outstanding considering he's not trained for the last three days.
"There's a lot to be said for their commitment and their desire to help the team."
As well as scoring the opener, Ciftci set up Armstrong's headed goal.
"You can see when he does things properly, he's a handful," McNamara said of the Turkish striker.
"I thought he was excellent along with everybody. As a team, especially after the performance last week against Aberdeen, when we were very disjointed, we were together. We got our rewards in the end."
Celtic substitute Stefan Scepovic had a goal ruled out for offside when his side were trailing 2-0, with television replays revealing the striker had been onside.
And McNamara said: "It looked quite tight from where I was."
Deila also gave his thoughts on the decision, saying: "That's disappointing.
"If we had gotten the goal earlier, we had a good chance to get some points in the end, but again, we put ourselves down then we have to struggle to get back into it."
The Norwegian was frustrated by Celtic's profligacy in front of goal.
"We lost the game because we weren't effective enough," he commented.
"We have created so many chances and, if we keep on missing them, you will lose points and today we did it.
"We haven't been effective enough in the last three or four games."
Defender Efe Ambrose struggled to contain Ciftci and was held off by the forward at the opening goal.
"It's not only him, it's with defending as a team," Deila said. "This is, of course, individual things.
"It's so important to show them out of the pitch and not give them the angles that he can open the goal, like we did in two cases when they scored."
And, on Griffiths, Deila added: "He was very good as a sub. He's been a goalscorer."