Martin O’Neill is preparing for the upcoming Celtic season with an eye on bolstering a defense weakened by injuries and potential player departures. While the club has yet to make any new signings this summer, the Parkhead manager expects the return of Cameron Carter-Vickers to provide a significant boost to the squad.

Carter-Vickers, who has been with Celtic for five years following an initial loan from Tottenham Hotspur that became permanent, has been widely regarded as the club’s top defender during his spell. However, the American center-back missed the entirety of last season under O’Neill’s caretaker management due to a serious Achilles injury sustained during a Europa League match against Sturm Graz in October 2025. The injury occurred just days before Brendan Rodgers’ departure and O’Neill’s subsequent takeover, meaning Carter-Vickers was unavailable throughout both of O’Neill’s interim stints last term.

The absence of Carter-Vickers was keenly felt at the back, with defensive frailties emerging as a result. Celtic often relied on Auston Trusty in defense, a player noted for being left-footed and not entirely comfortable in the position he was deployed. Former Celtic player and pundit Liam McNamara highlighted the difference Carter-Vickers’ return could make, not only defensively but also in set-piece situations. “He was a big miss ... Carter-Vickers is a good leader at the back, so you’re hoping that he’s going to be back to near enough what he was before he got injured,” McNamara said. He also pointed to how the team’s balance improved when full-back Alistair Johnston returned late in the campaign.

O’Neill faces the challenge of reinforcing the squad ahead of a season that may see the departures of Daizen Maeda, Reo Hatate, and potentially Arne Engels. While Carter-Vickers’ recovery is a key positive development, the manager will likely need to look to the summer transfer market to strengthen other areas. McNamara praised O’Neill’s ability to maximize the players at his disposal, particularly in the closing stages of the previous campaign, but stressed the importance of recruitment if Celtic are to progress to the Champions League group stage.

With Carter-Vickers on the verge of returning to fitness and O’Neill now firmly in charge, Celtic aim to restore defensive solidity as a foundation for success in the forthcoming season.