Manchester United centre-back Lisandro Martinez stepped up his injury recovery at the club's Carrington training complex on Monday, with the Argentina international closing in on a return to action.

The 25-year-old has only made six appearances for the Red Devils this season, with his last outing for the club coming against Brighton & Hove Albion in the middle of September.

Martinez initially underwent an operation in April to fix the fractured metatarsal that he suffered while facing Sevilla in the Europa League.

The centre-back returned for the start of pre-season training, but it was then confirmed at the start of October that he would need to undergo another surgery on the same issue, with a scan revealing that the initial operation was unsuccessful in terms of fully addressing the problem.

Red Devils head coach Erik ten Hag recently said that Martinez, who proved to be one of Man United's most important players last season, would not be available for selection before Christmas.

The South American was pictured at Man United's opening training session on Monday, with the defender initially featuring alongside his teammates before working individually.

Casemiro has also returned to training, with the Brazil international bidding to fully recover from the hamstring issue which he suffered against Newcastle United at the start of November.

Both players will again be missing for Tuesday's Champions League clash with Bayern Munich, while Tyrell Malacia, Christian Eriksen, Mason Mount and Amad Diallo will also again be absent.

Victor Lindelof remains a doubt due to the problem that forced him to miss the 3-0 home defeat to Bournemouth in the Premier League on Saturday afternoon.

"It's a condensed programme so we have a training [session later], so at this moment, I'm not sure about everyone, who's available for tomorrow" said Ten Hag during his press conference on Monday.

"But the question mark is on Victor Lindelof, whether he can make it or not. We have to wait and see until tomorrow."

Marcus Rashford and Anthony Martial are also both doubts, with neither player able to train on Monday due to illness.

Man United need to beat Bayern and hope that Copenhagen draw with Galatasaray in the section's other match in order to progress into the last-16 stage of the Champions League.

However, a win over the Bundesliga giants would guarantee that the Red Devils finish at least third, which would see them qualify for the Europa League knockout round playoffs.