Celtic claimed the championship on the final day of the 2025/26 campaign under Martin O'Neill, but a new data-driven study has delivered a damning assessment of their performances.

The Global State of Football report, produced by football analytics company PLAIER in collaboration with the University of St Gallen, handed Celtic the Premiership's only F grade for coaching efficiency. The champions recorded a score of -1.16, placing them bottom of the league in that category.

The findings are particularly striking given Celtic's remarkable recovery to secure the title ahead of Hearts and Rangers.

Rather than judging managers purely on results, the analysis measures how effectively teams perform relative to the quality of players at their disposal. And despite finishing top of the table, Celtic were judged to have underperformed against the standard expected from their squad.

The findings cover a turbulent campaign at Celtic Park that saw Brendan Rodgers depart, Martin O'Neill return to the dugout and Wilfried Nancy endure a brief spell in charge before O'Neill was restored.

The veteran manager eventually guided Celtic to a league and Scottish Cup double, but even that success was not enough to prevent the club from receiving the lowest coaching grade in the Premiership.

It represents a remarkable turnaround from the previous edition of the study, when Celtic received A grades across every category and were ranked first for coaching efficiency in Scotland. Celtic also topped the overall club index among 226 teams analysed in that earlier report.

However, the latest assessment was not entirely negative for Celtic. The club received an A grade for financial stability, reflecting their strong financial position despite the coaching efficiency concerns.

The report's findings are not a direct verdict on O'Neill's individual performance, with the figures assessing the club's output across the entire campaign and several managerial spells.