Martin O'Neill has more than enough experience to know the importance of today's derby in the context of the league and his position at Celtic Park in general.

Celtic have lost two games in a row. A 3-0 defeat away at Ibrox, which knocked them out of the League Cup at the hands of the Rangers, was followed by a 3-1 defeat at home against Ferencvaros.

So, a confidence booster is needed. But the next game is no easy one as Celtic will welcome the Rangers to Parkhead.

Derek McInnes' side will be riding high on confidence following that 3-0 win over Celtic merely a week ago.

On the other hand, there are a lot of question marks surrounding Celtic right now. And a lot of fingers are being pointed towards the board, who appear to have allowed the squad to be weakened for another summer transfer window.

O'Neill has never really been outspoken about Celtic's transfer activity, or its failures in the summer. But now, the manager has openly come out and admitted that they failed to bring in a replacement for Arne Engels.

Engels made a Championship record move to West Ham United this summer. But for one reason or another, a proper replacement was not found for him.

As reported by the Daily Record, O'Neill said about the matter: “I think that in an ideal world it would have been greater to have the likes of Arne Engels and that type of running power, and that’s really what we were trying to do when we knew that Arne was going to leave.

“So it didn’t materialise, but that’s something that we would certainly have to look at.

“Arne, I always felt he was going to be leaving anyway.

“Trying to get a like-for-like, we looked at a number of players who could do that.

“For one reason or another, it didn’t materialise. So yeah, he’s been a loss in terms of that running power he can give you.”

Obviously, the failure to do so has been a blow for Celtic. They ended up bringing in Oliver Sorensen on loan from Parma, but he has not convinced that he is the right man for the job.

On the other hand, the club were linked with a variety of midfielders for weeks, but none of those moves ended up working out.

Gvidas Gineitis is a perfect example of this. He seemed to be on Celtic's radar all summer but ultimately, a move did not end up happening.

It is worth mentioning that Celtic failed to make the Champions League once again. And that clearly had an impact on their transfer plans as the targets changed almost immediately.

Obviously, one can point a finger towards the players for failing to protect a 4-0 lead on aggregate with merely 60 minutes to go in the tie.

At the same time though, it could also be viewed as a failure on the part of the board, since they were not able to bring in proper replacements for key players in time to navigate the playoff tie against LASK.

O'Neill's comments are a positive as it goes to show that he is willing to openly speak about the club's failures in the media.