Celtic have stumbled into a defining Old Firm clash after suffering two damaging defeats in the space of five days.

Martin O’Neill’s side travelled to Ibrox last weekend with a place in the Premier Sports Cup semi-finals at stake, but they were swept aside by fierce rivals Rangers.

Dan Neil scored twice and Kevin Kelsy added another as Derek McInnes celebrated a commanding 3-0 victory in his first Old Firm game as Rangers manager.

Celtic struggled to match the home side’s aggression and rarely looked capable of changing the contest once they fell behind. It was their first domestic defeat of the campaign, and it also ended their hopes of retaining the trophy.

O’Neill needed an immediate response when Ferencvaros visited Celtic Park for Thursday’s Europa League opener.

Instead, the pressure only increased.

Mika Baur cancelled out the visitors’ opening goal, but Celtic could not build on that moment. Ferencvaros struck twice more to secure a 3-1 victory, with former Hoops winger Daniel Arzani completing another miserable night for his old club.

The final whistle was greeted by boos after Celtic conceded six times across the two matches.

O'Neill's side must now prepare to face Rangers again on Sunday, this time in the Scottish Premiership at Parkhead.

That leaves Celtic in a bizarre position, as they remain top of the league after winning each of their opening six matches, yet their displays in the biggest fixtures have suddenly created serious doubts.

Another defeat to Rangers would turn a worrying week into a full crisis.

Martin O’Neill faces growing Celtic pressure as two problems highlighted before Rangers clash

According to TEAMtalk, senior figures at Celtic are becoming increasingly frustrated with O’Neill and believe two major problems have not been solved.

The first concern is Celtic’s uneven level of performance.

Their perfect league record suggests everything is moving in the right direction, but the defeats to Rangers and Ferencvaros exposed weaknesses which were not as obvious against weaker Scottish opponents.

Celtic have looked unsure of their best shape, lacked intensity at important moments and struggled to control games when opponents have applied pressure.

The second issue surrounds the club’s summer recruitment.

Much of Celtic’s business was completed late in the window, leaving O’Neill with little time to introduce several new players before a demanding run of matches.

Record signing Kasper Høgh has yet to become the reliable focal point Celtic expected, with his performances against Rangers and Ferencvaros particularly criticised.

Camilo Duran and Haissem Hassan have offered only flashes of promise, while Baur found the net against Ferencvaros, but the new group has yet to form a settled unit.

That was never likely to happen instantly, but Celtic officials are reportedly concerned that the side still lacks a clear identity despite the season being well underway.

The report adds that O’Neill retains support from parts of the dressing room, although confidence has been damaged by the manner of the last two losses, and a defeat to the Gers could make his position 'untenable'.

Sunday’s derby could therefore have major consequences.

A victory would protect Celtic’s flawless league start, restore belief and give O’Neill valuable time to bring his squad together. Another defeat could persuade the board that the current direction is no longer working.

O’Neill has survived countless pressure matches throughout his career, but few have arrived with such a rapid change in mood.

Celtic were unbeaten domestically less than a week ago, but they now enter an Old Firm derby which could decide far more than three points.