That said, the Barclays Premiership leader also suffered their worst defensive display, and frailties at the back were alarmingly exposed at the Madejski Stadium, particularly from set-plays.
United need to get the balance right between defence and attack. It has become a major concern.
Bitter rivals Manchester City come into the game perhaps not firing on all cylinders; nevertheless, they remain unbeaten in the league and have amassed an impressive run of 37 Premiership games without a defeat at home.
So, Sir Alex Ferguson has much to consider ahead of the biggest game of the season this weekend, when the Etihad Stadium hosts the Manchester Derby, a fixture which promises to be a clash of the highest order.
Tactically, which formation should Sir Alex employ?
Much could hinge on the system that Sir Alex Ferguson chooses to utilise against the usually narrow midfield formations of Roberto Mancini.
On foreign turf, it's unlikely United will be bold enough to play two up-top, unless the claustrophobic midfield diamond is utilised.
The battle in the centre of the park will be absolutely critical, and the accomplished Yaya Toure, supported by Gareth Barry, could prove to be a threat that needs to be cancelled out.
Congesting the midfield may tactically be the most sensible option, so Sir Alex may elect a defensive midfield duo, assisted by Wayne Rooney dropping deep in a fluid 4-2-3-1 formation.
This would likely mirror a system that is popular with Mancini and create a fractious game with only the full-backs providing any width in what would be a tight affair.
Alternatively, the return from injury of Antonio Valencia and the return to form of Ashley Young could see some play down the flanks, set up in either a wider version of the 4-2-3-1 or a more standard 4-5-1.
One thing is for sure: It is becoming increasingly challenging to pre-empt the system United will employ ahead of a game. Whether this unpredictability is a positive or negative thing is open to debate.
David de Gea or Anders Lindegaard?
David de Gea has sat out the past few games after having his wisdom teeth extracted and suffering infection as a result. He is now available.
Anders Lindegaard came in and enjoyed mistake-free performances that rewarded him with a fifth consecutive starting berth against Reading.
Prior to the Reading game, Sir Alex Ferguson told Gemma Thompson of ManUtd.com, “I don't think Anders has done anything wrong since he came into the team. That’s what is keeping him in.”
However, Lindegaard looked indecisive against Reading and failed to come through for some challenging crosses. He did not seem in control of his defence, and this must concern Sir Alex.
Criticism of De Gea is much the same: dodgy on crosses, weak in the air, fails to organise his defence.
So the starting berth is up for grabs.
De Gea had the opportunity to put himself in contention by returning to the starting XI against CFR Cluj on Wednesday in the final group game of the Champions League.He performed reasonably well, but had little to do.
It will be a tough but potentially crucial decision for the manager.
Has Rafael reverted to type?
The young Brazilian is arguably United's player of the season so far. He has grown in maturity and is truly beginning to blossom in his fifth season for the Reds.
However, he was visibly uncomfortable against Reading, and his fatal flaws were once again exposed.
Rash in the challenge and lacking in positional understanding, Rafael was booked early on and was unceremoniously hauled off to be replaced by Chris Smalling, who returned some order to the right side of defence.
Some have argued he was a scapegoat for far worse defensive performances by Rio Ferdinand and Jonny Evans at the heart of the back four. But Rafael's place was not under threat all season, and that has now changed.
The return from injury of both Smalling and Phil Jones raises the question of who is United's best option at right-back. All three players have different qualities to bring to the table, but following the embarrassing inability to defend set-peices over the weekend, Sir Alex may opt for additional aerial prowess.
Only three clean sheets from 15 league games have been achieved this season, and the apparent hoodoo of conceding the first goal in 10 of those fixtures is causing serious concern in the corridors of Old Trafford.
Maybe a change is necessary.
That said, a settled back four is a desirable axis upon which to build a solid defence, and maybe the biggest game of the season requires a constant, at least from the start.
Should Paul Scholes or Ryan Giggs play?
Manchester United's midfield has come under much scrutiny this season, and the raging debate continues to surround the abilities of the aging Paul Scholes and Ryan Giggs.
Universally heralded as United legends, there is now much disagreement over whether they can continue to perform at the highest level.
Anderson, who had recently defibrillated a faint midfield heartbeat that was close to flat-lining, is now ruled out due to hamstring injury. Consequently, someone else needs to step up to the mark.
Many believe Scholes can no longer operate in a midfield pairing, particularly when alongside Michael Carrick, because there is simply not enough energy or dynamism on show.
Giggs has failed to express any sign of the golden days of bygone years. However, they both bring potentially critical experience to the fold.
There is the option of bringing Tom Cleverley into the mix; Darren Fletcher, rusty after spending a year on the sidelines due to illness, must also be in the manager's thoughts.
Much will depend on the tempo that Sir Alex will want to achieve, but with City's likely starting XI in the age bracket of 26-30 years, there can be no passengers.
Where should Wayne Rooney play?
Rooney has been utilised in much deeper positions this season. His talents in front of goal have been sacrificed for his work-rate and tenacity in the centre of the park.
It's a team game, and the arrival of Robin van Persie in close season has dislodged Rooney from his accustomed striker role and has seen him pick up responsibility for United's apparent shortfalls in midfield.
Many will argue that it's a criminal waste of skills, but it's worth considering the armoury of attributes that Rooney can bring to a playmaker role.
Manchester City will not expect him to play up top. If he did, it might set the Citizens off balance. Conversely, it may result in City taking devastating control of the midfield.
The balance is fine, but the safe option is to task him with assisting in deeper areas of the park while out of possession and offering him a free license to get forward when in control of the ball.
Sir Alex will be aware that the younger elements of the team need to fully mature or a steely midfield addition in the transfer window needs to be purchased, before Rooney can be unconditionally let off the leash to resume an out-and-out striker role.