In the second instalment of our five-part assessment of just how prepared Manchester United are for the upcoming Premier League season, we take a look at the defence.

If you missed yesterday’s review of the goalkeepers, you can find it here.

The intention of this series is to look at the United squad broken down into five different departments — goalkeepers, defenders, midfielders, attacking midfielders and strikers — and give each a grade based on quality and depth.

Defenders: Eric Bailly, Phil Jones, Marcos Rojo, Chris Smalling, Daley Blind, Luke Shaw, Timothy Fosu-Mensah, Antonio Valencia, Paddy McNair, Matteo Darmian, Axel Tuanzebe, Cameron Borthwick-Jackson

This is the area of the squad that needs the most work, and the area in which the most transfer activity can be expected between now and the end of the transfer window.

United had a solid defensive record last season, but don’t be fooled into thinking that that means United are good defensively; not by a long shot.

The relatively impressive tally of just 34 goals conceded in 38 Premier League games last season — joint-best alongside Tottenham Hotspur — was more a result of Louis van Gaal’s possession-heavy, risk-averse style of play than anything else.

Indeed, for most of last season, United lined up with Daley Blind, a midfielder-cum-left-back, in central defence. Blind coped admirably, and his accurate passing became an asset, but his positional sense is way off for the position, and his lack of physicality was exposed at times. Again, that’s not his fault, he was being played out of position, but if a sustained title challenge is to be mounted, a specialist defender is required.

In has come Eric Bailly from Villarreal, and the 22-year-old has looked particularly impressive during pre-season, but the Ivory Coast international is still some way off the finished product and should be afforded the time and patience of the fans to develop at his own pace, and acclimatise to his new surroundings.

Chris Smalling’s development was one one of the more pleasing take-aways from last season: the England defender finally started to deliver on the early promise he showed upon joining United from Fulham in 2010. But, during the latter part of last season, the rash decision-making and proneness to making costly errors began to creep back into his game. This season, Smalling should be given the opportunity to prove that he has found the requisite level of consistency to be a United player, but don’t be surprised to see José Mourinho dip into the market to find a reliable, experienced partner for the former Maidstone United player.

Luke Shaw’s return to fitness is one of the most encouraging factors for United fans going into the new season. The 21-year-old was in outstanding form before suffering an awful leg-break against PSV in the Champions League last September. The young England international was on course to become one of the best left-backs in the world, and hopefully he will be able to pick up where he left off before too long.

There is undoubtedly some dead weight within United’s defensive ranks, many of whom should be fearing for their future at Old Trafford.

Marcos Rojo was abysmal last season, and should be shown the exit door. Phil Jones has not significantly improved since joining the club as a teenager in 2011; he needs to prove his worth quickly or he too could be on his way out.

Matteo Darmian has been the subject of some transfer speculation over the summer, with reports suggesting the man signed from Torino a year ago could be set for a return to Serie A. Darmian made an impressive start to his United career but struggled to find his best form for most of last season. He is a versatile player with obvious quality, and should be given another season to show his best self at Old Trafford.

But if Mourinho doesn’t fancy Darmian -- which appears to be the case — that would leave Antonio Valencia starting at right-back. The Ecuadorian has done well in that role in pre-season, but we should be weary of reading too much into his performances in friendlies when the pressure is off. The club has been linked with a £25 million move for Monaco’s Brazilian full-back Fabinho, who would represent an upgrade on Valencia, but as it stands, it seems as though Mourinho prefers the former Wigan Athletic player to Darmian.

With Timothy Fosu-Mensah, Cameron Borthwick-Jackson and Axel Tuanzebe, United have a strong crop of young players capable of making the transition into the first-team — indeed, Fosu-Mensah may already be the best option for the right-back spot — and hopefully these players will get their fair share of game-time.

But, overall, United are lacking defensively, and at the present moment, without further investment, it is easily the weakest area of the squad. There is reason for hope though, as some minor tweaks could make a huge difference.

Position grade: C-