Former Celtic captain Paul Lambert says manager Martin O'Neill could resign following a 1-0 derby defeat to Rangers at Parkhead.
O'Neill stated after Sunday's loss that he will take time during the upcoming international break to consider his future at the Scottish Premiership club. The 74-year-old manager is facing mounting scrutiny after a dismal week that included three consecutive defeats across domestic and European competitions.
Lambert, who skippered Celtic under O'Neill during the manager's successful initial spell at the club, insisted Celtic would not sack the veteran manager. However, the former midfielder admitted he would completely understand if O'Neill decided to walk away voluntarily.

Mounting pressure on Parkhead icon
Celtic's downturn in form accelerated over the past week with back-to-back losses against Glasgow rivals Rangers alongside a Europa League defeat against Hungarian club Ferencvaros. The recent slump comes after an earlier European setback in the Champions League against Austrian side LASK, where Celtic squandered a four-goal lead.
Following Sunday's defeat at Celtic Park, O'Neill acknowledged that he was not immune from criticism. The veteran manager admitted he has questioned his own ability to turn the team's fortunes around and wondered whether it might be time to wrap it up.
Lambert believes O'Neill has earned the right to determine his own exit strategy given his extensive achievements in Glasgow. O'Neill returned to Celtic as interim manager twice last season following the departures of Brendan Rodgers and Wilfried Nancy, ultimately guiding the club to a Scottish league and cup double before signing a permanent contract in the summer.

Lambert stressed that O'Neill holds immense credit with the club's board and supporters. He pointed out that fans were calling for a statue to be built in O'Neill's honour not long ago, arguing that opinion should not swing wildly from one extreme to another after a single difficult week.
Celtic currently remain top of the Scottish Premiership table by two points, but the recent sequence of results has placed the club on the brink of another crisis.
Lambert hits back at player criticism
Lambert placed the blame for Celtic's current struggles firmly on the squad, arguing that the players must step up and take responsibility on the pitch. The former captain also delivered a sharp rebuke to defender Cameron Carter-Vickers following the centre-back's post-match comments.
Carter-Vickers claimed after the defeat to Rangers that Celtic's style of play had become too random and that the team was struggling to follow a consistent script on the field.

Lambert described the comments from Carter-Vickers as cringeworthy and completely out of order. He questioned why an established performer for Celtic would publicly criticize the manager's framework instead of resolving issues directly on the pitch.
Lambert argued that O'Neill has not altered his managerial approach from the methods that brought success last season. He insisted that experienced players must take charge during matches rather than relying on managerial intervention from the touchline when things go wrong.
Carter-Vickers insists squad remains behind manager
Despite highlighting the team's tactical struggles, Carter-Vickers insisted that the dressing room remains firmly supportive of O'Neill and his coaching staff.
The United States international defender acknowledged that it had been a brutal week for the squad, but noted that Celtic have navigated turbulent periods before and found a path through them.

Carter-Vickers stated that the playing group remains extremely grateful to O'Neill for rescuing last season and delivering silverware. He emphasized that the squad understands the frustration of the supporters and is working to rectify their performances.
The defender explained that Celtic are integrating numerous new signings into the squad this season. He drew comparisons to his own initial arrival at the club, as well as the period following Brendan Rodgers' return, noting that both transitional phases required time before the team reached peak performance levels.
Celtic look to international break to regroup
Carter-Vickers stressed the necessity of maintaining consistency and clarity in the team's objectives despite recent setbacks. He noted that while results may not always be perfect, staying committed to a clear process consistently leads to positive outcomes.
Celtic now enter the international break searching for stability as O'Neill weighs his future in charge. The club's hierarchy tentatively applauded the team off the pitch following Sunday's defeat, reflecting the uneasy atmosphere surrounding Parkhead.
O'Neill's previous spell in charge of Celtic between 2000 and 2005 stands among the most celebrated eras in the club's modern history. Supported by Lambert in midfield, O'Neill led Celtic to multiple domestic trophies and the 2003 UEFA Cup Final. Whether O'Neill continues his second permanent stint at Celtic Park will be determined before domestic fixtures resume.

