Celtic have five managers to replace Martin O’Neill as Roy Keane is spotted at Parkhead

Celtic could be forced to consider their options in the managerial market after Martin O’Neill raised doubts about his future following Sunday’s derby defeat to Rangers.

Ryan Naderi scored the only goal of the game as Rangers claimed another victory over their Glasgow rivals, less than two weeks after defeating Celtic in the Premier Sports Cup quarter-finals at Ibrox.

O’Neill admitted after the final whistle that he would take time to consider whether he remains the right person to lead Celtic.

The experienced manager questioned whether he is still able to have the desired impact on the team and acknowledged that his age could become a factor in the decision.

If O’Neill does decide to leave, Celtic could begin searching for a successor. Several managers could potentially enter the conversation.

Thomas Frank

The former Brentford manager could be an attractive option for Celtic. Frank built an impressive reputation during his time in charge of Brentford before moving to Tottenham.

His spell in north London did not go as planned, but his work at Brentford established him as one of the most highly regarded coaches in English football.

Robbie Keane

The former Republic of Ireland striker has previously been linked with the Celtic job, including earlier this year when Wilfried Nancy left his position.

Keane did not get the job at that time, but his managerial record has since developed further. He has guided Maccabi Tel Aviv and Ferencvaros to domestic titles and could once again be considered if the Celtic position becomes available.

Kieran McKenna

Convincing McKenna to leave his current situation could prove difficult, but the former Ipswich boss would inevitably attract attention if Celtic begin looking for a new manager.

However, there would also be a significant financial consideration. Ipswich are reportedly still due around £8million in compensation if McKenna takes another job before the end of the season.

Shaun Maloney

Maloney has long been regarded as a potential future Celtic manager and already has a strong connection with the club.

He enjoyed a successful playing career at Celtic and also worked as part of O’Neill’s coaching staff, giving him an understanding of the club and its expectations.

The question would be whether Celtic want to continue with a familiar coaching structure or take the opportunity to pursue a completely different direction.

Roy Keane

Keane’s presence at Sunday’s Old Firm derby has inevitably added to the speculation surrounding his name.

The former Celtic midfielder was spotted at Parkhead watching the match, prompting questions about whether he could become a candidate if O’Neill decides to step down.

Keane has extensive experience as a player and pundit, but his last managerial position came at Ipswich more than a decade ago.

If O’Neill leaves, Celtic would therefore have several potential routes to explore before deciding on their next manager.