Celtic boss Neil Lennon has conceded that his side are in a tough tile fight after losing 2-1 at home to Rangers in the Old Firm derby.

The champions missed a penalty before Ryan Kent put Rangers in front and though Odsonne Edouard equalised before half-time, Nikola Katic's header gave the visitors their first win at the stadium since 2010.

The result means that Celtic's lead at the top of the table is cut to two points and Rangers hold a game in hand.

Lennon said there was no doubt that meant a tough competition when the Premiership resumes after the winter break.

"It means it's game on," he said. "We would have had an eight-point cushion or a five-point cushion.

"Now if Rangers win their game in hand they'll have a one-point cushion so there's nothing in it.

"It's a test of their character now, which is good.

"They need to reset and get a rest because it's well deserved and they've been on a brilliant run.

"It's not the time to be over-critical. We've lost the game but there's plenty to play for.

"We've got time to think about it now."

The Celtic boss said he couldn't put his finger on why his side hadn't been at their best but said they hadn't made the most of some key chances in the game.

"We didn't start well at all," he said. "We had good spells up until half time and then we came off it again.

"It's a poor goal to lose, the second one. A free header in our box. Then you're chasing the game and we had good chances.

"We had one cleared off the line, we missed a penalty and they are big moments.

"Overall we didn't play well. We didn't deserve to lose it but we didn't deserve to win it either."