Martin O'Neill, the man who delivered a double few thought possible last season and very nearly lifted the Uefa Cup in 2003, has wondered out loud whether now is the moment to walk away from Celtic — even with the club still top of the Scottish Premiership.

Speaking in the aftermath of Sunday's derby defeat to Rangers — a second loss to their arch-rivals in the space of a week, with a home European defeat to Ferencvaros wedged in between — the 74-year-old admitted he would spend the coming days reflecting on whether he is still the right man for the job, and joked that he would be "110 years old in two years' time".

"I genuinely will reflect and see," O'Neill said. "It's a matter of whether I can help the team. The manager is supposed to be able to do that. I will look at that this week.

"I think every single time something crops up and things don't go so well, age plays a part. And, do you know what, they might be right. I'll be 110 in two years' time so it might be time to wrap it up.

"I will reflect on the games and speak to the board. You never know, they may well want to speak to me. I'll try to get a couple of days away and see how it goes."

An all-time great weighing his legacy

O'Neill's status as one of Celtic's all-time great managers is surely secure. He salvaged the Scottish Premiership and Scottish Cup from the potential wreckage of one of the club's most tumultuous seasons last term, and in 2003 came agonisingly close to the Uefa Cup against a Jose Mourinho-inspired Porto side who won the Champions League the following season.

Lending credence to the notion that O'Neill is embarking on a period of proper soul-searching, he referenced last season's dramatic last-day decider, in which Celtic won the title in the final few minutes of the last league game.

"The game against Hearts was probably one of the great moments of my managerial time. And I've had some really good moments," he said. "While that was good and I was delighted to get that opportunity, all the time I was still thinking about whether you can still have the energy and the desire — the things that I say to the boys every Friday — so I'll have a look at that and we'll see."

The question now hanging over the club is whether O'Neill might decide to protect his fine legacy by walking away while the side is still top of the Premiership.

How has it gone so wrong, so quickly?

It is worth remembering that half an hour into the second leg of their Champions League play-off in August, Celtic were 4-0 up on aggregate against LASK in Linz and seemingly cruising to the league phase of European football's elite competition. The collapse within that game — and the humiliating exit that followed — appears to have left an indelible scar on the players and management team alike.

The four Premiership wins that followed were largely unimpressive, three of them single-goal victories against Falkirk, St Mirren and St Johnstone. When the pressure was truly on — against Rangers twice and Ferencvaros — Celtic simply folded.

Recruitment questions mount

Questions have been asked by a section of the club's support about the quality, breadth and timing of the summer recruitment, and former Scotland international James McFadden remains unconvinced.

"They haven't actually added to the squad in terms of numbers or real quality," he said on Sky Sports. "They've just replaced what left."

O'Neill has tried to find a way to accommodate big-money signings Camilo Duran and Kasper Hogh into the side without much success, and has used a series of different midfielders to try to reinvigorate the heart of his team. He even abandoned his wingers entirely for Sunday's league derby, fielding five defenders and pushing full-back Kieran Tierney further forward. All to no avail.

'They were smashed' — pundits round on Celtic

Chris Sutton, who played under O'Neill during the manager's first spell at the club, was deeply unimpressed by what he saw.

"It wasn't a close game," he said on Sky Sports. "There was a massive gulf. I can't remember a Celtic team getting such a doing from a Rangers team at Celtic Park.

"Rangers were a team and Celtic weren't. They knew their next pass and Celtic didn't. Rangers were better in every department. They were smashed and that's the concern.

"They have big problems, some self-inflicted. They've lacked legs and physicality in the middle of the park. This has been a big issue all season. Callum McGregor's another year older, can't get about the pitch like he used to."

Yet Sutton still believes O'Neill has the stomach for the fight. "Martin will have to come up with something. I loved him as a manager when I was at the club. He is getting on a bit but, as a guy, I still think he has the fight for it."

That sentiment is shared by Sutton's former team-mate Neil Lennon, who knows O'Neill better than most — and knows how heavily the mantle of Celtic manager can weigh.

"He's hurting, he's smarting about it," Lennon said on Sky Sports. "He'd want to find the answers. The break's come at a good time for him — recuperate, get some sun and re-think about the whole thing. He still feels he's got the energy to do it.

"When you get a week like this — not only defeats but the manner of the defeats — he knows himself more than anyone there's going to be a lot of scrutiny, criticism and introspection."

What the fans are saying

The Celtic support has been scathing. Lee wrote: "This is it for MON — his starting XI looked weak in midfield and proved to be. What he and the coaching staff have done to our big summer signings after bright starts is a worry. And the general fitness is telling, too."

Alec questioned the manager's assessment of the derby: "What game was MON watching, to say it was a close game? Wow. It's quite obvious MON and the coaches don't know the best 11 or a formation for them."

Kev added: "You can see O'Neill throwing the towel in here soon. I don't blame him. There's something smouldering at the club. This international break has come at the right time for Celtic. Dermot [Desmond] will be phoning his mate Pep for a hand at this rate."

Wayne said: "Let's be honest, getting beat is part of the game, as a fan you can accept that. What as fans you cannot accept is not giving it all, and that's the problem Celtic have at the moment — getting beat by average teams three games in a week. Shocking performances."

And Danny warned: "The board will keep O'Neill on as they think the fans won't turn, but another loss and it will become very toxic and all the good O'Neill has done will be forgotten."

What happens next?

O'Neill says he will review the games, take a couple of days away and speak to the board, who he suggests may want to speak to him. With the international break offering a rare moment of respite, the 74-year-old must decide whether the energy and desire he demands of his players every Friday still burn within himself — or whether, as he put it, it is finally time to wrap it up.