Celtic's lack of improvement behind decision to leave, says Ronny Deila

Ronny Deila says his inability to improve Celtic during his time at the club has 'killed him inside'.

The Norwegian, who took over from Neil Lennon in the summer of 2014, announced he was leaving in the summer just three days after the Scottish Cup semi-final defeat to Rangers.

Deila led the club to the Scottish Premiership and League Cup double in his first year and the Hoops currently boast an eight-point lead over Aberdeen with five games remaining.

Speaking ahead of the first post-split fixture against Ross County on Sunday, the former Stromsgodset manager said: "It has been a tough week, there has been a lot of thinking and it hasn't started this week either.

"I have been thinking about this for a while because I haven't felt the team has got the results they should have and, maybe more importantly, the performance and improvement I wanted.

"When I came in to the job, I talked about improving the team and playing attractive football and I think the last six months we haven't had the improvement that we need."

And with the speculation on his future with the club now over, Deila admits he is looking forward to bowing out with a second successive league championship.

"Improvement is one of my biggest values and when you don't get it, it kills me inside and I lose energy with that.

"I don't think there has been a lot of improvement and when you don't get improvement, the outside pressure is going to get harder and harder as well.

"I have no problem dealing with that, I have been sitting in this room a lot of times and there has been a lot of difficult questions.

"That is not the problem, the problem is when you don't get improvements and the things you said you wanted to create when you came in the door, you haven't created.

"One of the reasons we haven't had that improvement is because of the pressure and speculation around me all the time.

"That is why I think it is best for the club that new energy is coming into the club next season and now we can really focus on winning the five games and getting five-in-a-row. It is going to be a huge thing for me, the players and the whole club, this is why the decision has been made."

And Deila has rubbished suggestions he was not in charge of the club's transfer policy during his near two-year spell at the helm, insisting he takes full responsibility for the current strength of the squad.

"One, I signed the players so don't think about that. There is not one player here that I haven't said yes to. Two, I knew what I went into when I took the job," said Deila, who brought 22 players to the club during his 22 months in charge.

"This club want to be drifted in a positive way and have a positive economy and you have to drift in those circumstances.

"Everything that is coming into the club is going out of this club. That was said before I came here and it's the same now. It is the philosophy of the club and I think it's a very, very good thing.

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"I have had good communications with the club and Peter [Lawwell]. I am not a bitter man. I was given a chance but I felt that lately we haven't had the development that we wanted in the team."