The defensive problems that have plagued Louis van Gaal ever since he took up the reins at Old Trafford show no sign of abating. The failure to replace departing veterans Nemanja Vidic, Rio Ferdinand and Patrice Evra has been crudely exposed by a succession of injuries and suspensions that have meant Van Gaal having to repeatedly change his backline.

In all, 11 players have featured in defense for the Premier League side less than three months into the season. In United’s Manchester derby defeat to Manchester City on Sunday, both of Van Gaal’s center-backs left the pitch early, with Chris Smalling earning a red card and a one-match suspension and Marcos Rojo suffering a dislocated shoulder that could see him miss up to three months. It means midfielder Michael Carrick could partner 19-year-old Paddy McNair against Crystal Palace on Saturday.

Given not only the dearth of options but the questionable performances of many of his defenders when they have been fit, there is widespread anticipation that Van Gaal will address his defense in the January transfer window. One name in particular continues to be linked with a move to Old Trafford.

Ron Vlaar was a key figure for Van Gaal when the United boss guided the Netherlands to third place at the 2014 World Cup and the Daily Mirror is the latest source to report that a reunion could be in the offing. The 29-year-old’s contract with Aston Villa is set to expire next summer and both United and Arsenal are said to be keenly monitoring the situation. According to the Mirror, Villa would be willing to listen to offers of around £12 million in January -- a figure it is difficult to imagine United matching  given Vlaar’s age and the fact that he could walk away for nothing at the end of the season.

Manchester United are also reported to have an eye on the contract predicament of West Ham center-back Winston Reid. Like Vlaar, the New Zealand international is set to be a free agent next summer. And the latest information out of West Ham is that discussions over a renewal have stalled.

“Things are not really progressing but we’re hoping his agent will come to a meeting in the next few weeks,” a spokesman said, according to the London Evening Standard.

Reid, 26, has become a key figure for West Ham in recent seasons and is said to be looking to cash in on his performances with a contract of £80,000 a week.

The displays of Marouane Fellaini have been a key part of Manchester United’s recent improved performances, with the Belgium adding some much-needed steel to the team’s midfield. Fellaini’s return to form may lead Van Gaal to decline the chance to bolster what had previously been a lightweight midfield in January.

Another of Van Gaal’s World Cup squad, Nigel de Jong, has been seen as a transfer target for Manchester United since the summer. Yet, although the former Manchester City hard man will be out of contract with AC Milan after this season, he has indicated his desire to remain with the Italian giants.

“My contract is a question for [Adriano] Galliani,” he said, according to Sky Sports. “I’m happy here in Milan. I don’t see any problems for a renewal. Let’s hope we still have time.”

The Daily Express writes that United instead have their sights set on Benfica midfielder Enzo Perez, The 28-year-old recently converted from a right-sided role to become a key central midfielder for the Lisbon giants as well as impressing for Argentina at this summer’s World Cup. According to the Express, Van Gaal wants United to meet his £23.5 million release clause in order to deploy him on the right side of his midfield diamond. Yet, given Fellaini’s recent performances and the presence of Ander Herrera, such a move would be something of a surprise.