Martin O’Neill is facing growing questions over his tactical decisions after Celtic’s painful 2-1 defeat to Celta Vigo, with the decision to introduce Oliver Sørensen late in the match prompting fresh debate about the manager’s use of his available options.

Celtic supporters were already frustrated after watching their side surrender a second-half lead at Celtic Park. Mika Baur put the Hoops ahead shortly after the interval, but Javi Rodríguez struck twice in quick succession to hand the Spanish visitors all three points.

The defeat was Celtic’s third consecutive loss in the Europa League league phase, leaving the club under mounting pressure to turn its European campaign around.

Yet the result has also intensified scrutiny of O’Neill’s decisions from the dugout. Sørensen did not enter the match until the 79th minute, replacing goalscorer Baur after Celta had already completed their comeback.

For supporters who believe Celtic’s midfield needs a different profile and greater energy, the timing of that substitution raises an obvious question: could Sørensen have been introduced earlier, when the match was still there to be rescued?

OLIVER SØRENSEN’S LATE INTRODUCTION SPARKS DEBATE

Sørensen’s introduction came during a period when Celtic were desperately searching for a way back into the contest.

The midfielder replaced Baur in the 79th minute, approximately eight minutes after Rodríguez scored his second goal. Sebastian Tounekti also came on for Camilo Durán around the same time as O’Neill attempted to change the team’s attacking options.

The timing is important because Celtic had already lost control of a match they had been leading.

Once Rodríguez made it 2-1, the challenge was no longer simply about protecting an advantage. Celtic needed to find a way to break down Celta’s defensive organisation while avoiding further mistakes at the other end.

Introducing Sørensen earlier might have given him more time to influence the contest, depending on the role O’Neill wanted him to perform. A midfield change before the equaliser could also have been considered if the manager believed Celtic were beginning to lose control of the game.

However, substitutions are rarely straightforward. The manager must consider the players’ physical condition, tactical responsibilities and the risks involved in changing the team’s structure.

The legitimate question is whether O’Neill recognised the need for a midfield adjustment early enough.

For frustrated supporters, seeing Sørensen introduced only after the match had turned against Celtic will inevitably fuel doubts about the timing of the decision.

WHY CELTIC’S MIDFIELD NEEDS A DIFFERENT APPROACH

One of the most concerning aspects of Celtic’s defeat was the difficulty they experienced controlling the match against a Celta Vigo side that enjoyed more possession.

Celtic recorded 44 per cent possession compared with Celta’s 56 per cent, while both teams registered four shots on target. The visitors also produced significantly more attempts overall, underlining how much pressure the home side faced.

Those numbers suggest that Celtic had moments of attacking promise but struggled to dictate the overall rhythm of the contest.

A midfield capable of retaining possession, winning second balls and helping the defence reset can be particularly valuable in European matches. When an opponent begins building momentum, composure in the centre of the pitch can prevent one difficult spell from becoming a prolonged defensive struggle.

That is where Sørensen’s potential involvement becomes an interesting talking point.

Supporters who want him involved more regularly will argue that he deserves an opportunity to offer something different in midfield. Rather than continuing with an approach that has produced disappointing European results, Celtic could benefit from examining whether alternative combinations would provide better balance.

But the solution is not necessarily to select Sørensen simply because the team lost. His effectiveness would depend on the role he was given, his understanding with his teammates and whether his strengths addressed the specific problems Celtic encountered.

The important point is that O’Neill must find a midfield combination capable of providing greater control when Celtic are under pressure.

MARTIN O’NEILL’S SUBSTITUTIONS DESERVE CLOSER SCRUTINY

O’Neill’s decisions are attracting attention because the same broad problem has continued to appear in Europe: Celtic have struggled to turn promising situations into positive results.

Against Celta Vigo, Celtic took the lead but were unable to maintain their advantage. Rodríguez equalised in the 68th minute before scoring the winner three minutes later.

The manager responded by introducing Kasper Høgh for Haissem Hassan in the 73rd minute. Sørensen and Tounekti followed later, replacing Baur and Durán respectively.

There is a reasonable argument that Celtic needed changes earlier, particularly if O’Neill believed his team was becoming increasingly vulnerable in midfield.

Fresh legs can help a team close spaces, improve its pressing and retain possession during difficult periods. A timely tactical adjustment can also disrupt an opponent that has begun to dominate the flow of the match.

However, it would be unfair to assume that earlier substitutions would automatically have prevented Rodríguez’s goals.

The equaliser came from a set-piece situation, while the winning goal followed a period of pressure around Celtic’s penalty area. Those incidents also demand better defending, clearer communication and more effective decision-making from the players.

O’Neill must examine the entire performance rather than treating substitutions as the sole explanation for the defeat.

Nevertheless, when a team repeatedly struggles in the same areas, the manager has a responsibility to consider whether his selection and in-game adjustments are helping or hindering progress.

THE MISSED OPPORTUNITY TO CHANGE THE GAME

Celtic’s second-half lead offered O’Neill an opportunity to manage the contest from a position of strength.

Mika Baur’s 47th-minute goal gave the hosts something to protect, while Liam Scales came close to doubling the advantage when his header struck the crossbar.

At that stage, Celtic had a chance to build on their lead and force Celta Vigo to take greater risks.

Instead, the visitors equalised and quickly scored again.

The speed of that turnaround raises questions about whether Celtic responded effectively as the match began to slip away.

A manager does not always need to make an immediate substitution after conceding. Sometimes the best response is to trust the players already on the pitch to restore their organisation.

But when the team’s structure is visibly struggling, waiting too long can leave limited time to make a meaningful difference.

Sørensen’s late introduction has therefore become part of a wider discussion about O’Neill’s in-game management. Supporters are not simply questioning one substitution; they are asking whether the manager is reacting quickly enough when Celtic’s weaknesses become apparent.

CELTIC’S EUROPEAN RECORD LEAVES LITTLE ROOM FOR EXPERIMENTAL THINKING

Celtic’s latest defeat makes their European situation increasingly uncomfortable.

After losing their opening matches against Ferencvaros and Benfica, the Hoops needed a positive result against Celta Vigo. Instead, they remain without a point after three league-phase fixtures.

That record places enormous importance on the remaining games.

O’Neill cannot afford to keep repeating an approach that fails to deliver results, but neither should he make changes simply to satisfy supporters after a disappointing night.

The challenge is to identify the adjustments that are most likely to improve Celtic’s performances.

That could mean giving Sørensen a larger role, changing the midfield structure, improving defensive protection or finding a better way to control possession when the opposition begins applying pressure.

The manager must assess those possibilities carefully and make decisions based on what the team needs rather than what will generate the least criticism.

With qualification hopes under pressure, Celtic need a clearer plan for turning competitive spells into victories.

SHOULD OLIVER SØRENSEN START THE NEXT MATCH?

Sørensen’s limited involvement naturally raises the question of whether he deserves a more prominent role in the next game.

There is a case for giving him a greater opportunity if O’Neill believes his qualities can address the midfield’s current shortcomings. Starting him would allow the coaching staff to assess his contribution over a longer period rather than relying on a brief appearance late in a match.

It would also give Celtic another opportunity to evaluate different midfield combinations and determine which players work best together.

However, selection should be based on more than the frustration surrounding the Celta Vigo defeat.

O’Neill must consider Sørensen’s training performances, fitness, tactical discipline and ability to carry out the responsibilities required by the team’s system.

If those factors support a larger role, keeping him on the sidelines for extended periods would invite understandable questions.

If the manager believes another combination is better suited to the next opponent, he should have a clear footballing explanation for that decision.

What Celtic cannot afford is to ignore potential solutions while the same problems continue to undermine their European performances.

THE PRESSURE IS NOW ON O’NEILL TO FIND ANSWERS

O’Neill remains responsible for finding a way to improve Celtic’s results, and that responsibility extends beyond the decisions made during one match.

The manager must decide whether his current midfield combination provides enough control, whether his substitutions are arriving at the right time and whether his tactical approach is giving the players the best opportunity to succeed.

Sørensen’s late introduction is a reasonable subject for debate, particularly because Celtic were chasing the game when he entered.

But the larger issue is whether O’Neill can make the necessary adjustments before another European opportunity disappears.

Celtic supporters have every reason to be disappointed after watching their team surrender a lead at home. They will want to see evidence that the coaching staff has identified the problems and is prepared to respond.

The question is no longer simply why Oliver Sørensen came on so late. It is whether Martin O’Neill can find the right combination of players and tactics to stop Celtic’s European campaign from slipping further away.