Manager Ronny Deila labelled Celtic's 2-1 home defeat to Motherwell on Saturday as a bad day at work as their lead at the top of the Scottish Premiership was cut to just a point.

The Hoops had taken the lead through a 49th minute deflected Nir Bitton strike before Louis Moult equalised four minutes later.

Moult got his second from the penalty spot after Australian striker Scott McDonald had been clipped by Jozo Simunovic in the box to seal a first win for Motherwell at Celtic Park since 2008.

Deila said he was surprised at his side's poor defensive performance and admitted the result was a fair reflection of the game.

"Of course I didn't expect that. It was very, very disappointing. Overall it was a bad day at work and in the end I think we deserved to lose," Deila said.

"Today was a bad performance. That's something we have to admit and we have to turn it around.

"I think in the first half we didn't play quick enough and we were too narrow up front.

"In the second half I think we started well and got our goal and had a couple of chances. But then we played way too open and were not disciplined enough. If you do that then you get punished by the counter attacks and that happened today.

"When you play games the most important thing is the defence. You have to work really hard defensively and be compact and we have done that in a lot of games domestically.

"In the last few games we haven't conceded a lot of goals or chances but today we were way too open and then you give the opponent the space to play in and you get punished in the end.

"We had our chances but when you play so open you will get punished so that's something we need to talk to the defenders about and sort out for next Sunday."

Aberdeen's 4-0 demolition of Kilmarnock moves them to with a point of the Hoops, who haven't won at Celtic Park since October 31 following Europa League defeats to Molde, Ajax and a goalless draw with Kilmarnock.

"I don't think we have lost domestically at home since February but we shouldn't lose at home," Deila, who has come under pressure this season for a disappointing early exit from the Europa League, said.

"We have to build up Celtic Park as a very hard place to come. We have had a lot of good games here but lately we haven't opened up teams and scored enough goals."

The result provided some redemption for Motherwell manager Mark McGhee whose last visit to Celtic Park five years ago while in charge of Aberdeen ended in a record 9-0 defeat.

"I'm trying to keep a little bit of a lid on it as it's just one result. It's a great result but we've got a long way to go," McGhee, in his second spell in charge of Motherwell, said.

"It was a great performance and I think we thoroughly deserved to win.

"It's one of a sequence of three performances now and we are starting to see a bit of consistency.

"I've been delighted with the way the team has shaped up in the last couple of games.

"I thought if we could produce that kind of performance we could give them a game here.

"The fact that we've gone and won it is fantastic."