Javier Hernandez Manchester United Nicolas Otamendi Valencia
Nicolas OItamendi [R] is a January transfer target for Manchester UnitedReuters

Angel Di Maria has been in sparkling form for Manchester United after signing from Real Madrid for a British transfer record fee, and Radamel Falcao will score the goals soon enough, undoubtedly. However, the major concern for Manchester United manager Louis Van Gaal remains at the other end, with his defence looking more porous than a sand castle in a rainstorm.

To address that particular issue, Van Gaal is already looking at potential defensive signings for the summer transfer window and the Dutchman has reportedly zeroed in on Valencia's Nicolas Otamendi.

The Argentina international has been linked with a move to Chelsea and Manchester City in the past, but Manchester United are determined to beat out competition from their English Premier League rivals, according to the Daily Express.

Otamendi only joined Valencia earlier this year, before being loaned out to Brazilian club Atletico Mineiro for a short stint.

The 26-year-old, however, is seen as an important player for Valencia this season, and reports in Spain suggest, the La Liga side will not let go of the defender for anything less than his buyout clause – which stands at a whopping £40 million.

While Manchester United flexed some serious muscles in the transfer market this summer, it is unlikely that Van Gaal and Ed Woodward will be willing to shell out £40 million for the defender, who cost Valencia just £9.5 million in January.

However, what is certain is that Manchester United need strengthening in the central defensive positions, especially with Phil Jones, Chris Smalling and Jonny Evans, who has been pretty unconvincing this season, all remaining injury-prone.

Manchester United cannot hope to outscore their opponents every time, as they found out so dramatically against Leicester City on Sunday. However, Wayne Rooney, the club captain, is someone who still very much believes in his side's quality and ability to win silverware this season.

"There seems to be a lot of people who have written us off because of Sunday's result, but I don't see it that way," the striker said on Facebook. "When I look around our dressing room and see the quality we have and the manager's unbelievable attention to detail I have no doubts this team will be successful."