This will happen if the club failed to sign a new centre-back before the transfer window closes.
The former Chelsea manager is desperate to recruit an established, world-class centre-back to bolster his back-line and provide a solid platform for more attacking, expansive football.
Tottenham defender, Toby Alderweireld has been his preferred choice and United are hoping to negotiate a fee below Spurs’ £75million valuation having been quoted the same record-equalling figure for Leicester’s Harry Maguire.
The Independent, UK, reports that the former Real Madrid boss was unhappy with his current options.
The Portuguese is now exploring the possibility of moving Matic back to centre-half.
Matic has played there earlier in his United career, notably in the second half against Burnley on Boxing Day last season.