It’s a big blow for Michael Carrick.

Michael Carrick’s fledgling reign at Manchester United has taken an unwelcome turn after Lisandro Martínez suffered a fresh training setback, placing the Argentine defender on an open-ended lay-off and deepening a defensive crisis that threatens to derail the club’s push for Champions League qualification.

Martínez, who initially strained a calf last month and was expected to miss only a handful of days, has already sat out United’s last three fixtures. The latest hitch in his rehabilitation has forced the club’s medical staff to rip up his return schedule and design a more conservative recovery plan, mindful of the cautionary tale provided by Matthijs de Ligt.

De Ligt’s saga underscores the stakes: the Netherlands centre-back has not featured since November after a back complaint that was first pencilled in as a short-term absence. Sunday’s visit of Aston Villa will mark his 18th consecutive game missed, with his lay-off now stretching past four months and no firm comeback date in sight.

United’s revised approach to Martínez is rooted in a determination to avoid a repeat of De Ligt’s prolonged absence at a juncture where dropped points could prove fatal. Defeat to Newcastle last time out tightened the battle for a top-four berth, leaving Carrick little margin for further disruption.

The interim manager’s switch from Ruben Amorim’s back three to a 4-2-3-1 offers scant consolation; with both Martínez and De Ligt unavailable, Carrick is down to two established senior centre-backs. Harry Maguire and 20-year-old Leny Yoro have formed the makeshift pairing, yet the drop-off in experience behind them is stark.

Ayden Heaven, 19, is the next cab off the rank. The former Arsenal academy graduate flashed promise under Amorim but has seen only eight minutes of action across three cameos since Carrick took charge, and lapses that crept into his game late in the previous regime have curbed his involvement. Academy product Godwill Kukonki has been summoned to bolster numbers, but the 18-year-old remains untested at senior level.

United’s hierarchy fear that an injury to either Maguire or Yoro would push the rearguard from stretched to threadbare, potentially compromising a run-in that includes meetings with Villa, Liverpool and Chelsea. With De Ligt’s season in jeopardy and Martínez’s return date now nebulous, Carrick must balance short-term results with the long-term health of his remaining defenders.

The club’s revised medical protocol for Martínez emphasises gradual reintegration, even if that means absorbing his absence for several more weeks. In a season where every point is precious, United can ill afford another gamble that backfires.