Sir Alex Ferguson's 'My Autobiography' is fastest seller ever PIC: Reuters
Sir Alex Ferguson bowed out after winning Manchester United's 20th league title

Sir Alex Ferguson announced his retirement as Manchester United one year today, a decision that heralded a tumultuous 12 months for the Premier League champions.

Bowing out in characteristicly swashbuckling manner - a 5-5 draw against West Brom - Ferguson had already secured the club's 20th English title, widening the gap between arch rivals Liverpool and their perch to two championships.

But after the ticker tape had settled, the empire Ferguson had built, trophy by trophy, dramatically receded into the background.

Hand-picked successor David Moyes was recruited ahead of José Mourinho to lead United as it entered a new post-Ferguson era but when results went from bad to worse, it was his head that ultimately rolled.

IBTimes UK looks at some of the defining moments of United's annus horribilis.

Mike Phelan
Mike Phelan (L) was removed from the coaching staff at Manchester United along with Eric Steele.

Backroom clearout - one of Moyes's first decisions is considered his most fatal. In his later years as manager, Ferguson left much first team training to trusted consigliores. However, once Moyes got his feet under the United desk he disbanded the trusted cohort, firstly by sacking Mike Phelan and goalkeeping coach Eric Steele - who learned Spanish to better communicate with David De Gea - and then by not offering Rene Meulensteen - a favourite of top scorer Robin Van Persie - a suitable position in the new hierarchy.

Fellaini faltered as a Manchester United playerManchester United

Summer failings- new chief executive Ed Woodward was given a baptism of fire when he oversaw a summer bereft of transfer deals. The champions had built a reputation for conducting their transfer affairs largely behind the cloak of Old Trafford but after being rejected by Cesc Fàbregas, United were left scrambling for a midfielder and ended paying £27 million for Belgian flop Marouane Fellaini.

David Moyes Sacked as Manchester United Manager
Manchester United lost a record seven home league games this season

Loses pile up - after a narrow 1-0 loss to a rejuvenated Liverpool, United were then battered 4-1 by Manchester City in Moyes's first derby and embarrassed at Old Trafford by West Brom, who beat Moyes's side 2-1. Newcastle and Everton then both took all three points at United's home in December.

Roy Keane
Roy Keane berated the Manchester United players for letting down former manager David MoyesGetty

Olympiakos - already out of both domestic cups and written off in the Premier League, the Champions League became United's only real chance of silverware. Given the favourable tie against Greek champions Olympiakos, Moyes's side put in their most pusillanimous performance of the year - a category rich with entrants - in a 2-0 loss maligned by former captain Roy Keane.

Moyes Out banner
A group of Manchester United raised £900 to fly this banner over Old Trafford

Moyes Out - enough was enough for a section of the Old Trafford faithful. A disgruntled group clubbed together to pay £900 for a banner reading 'Wrong One - Moyes Out' - in reference to the Stretford End's 'Chosen One' banner - to whirl overhead prior to the home league match against Aston Villa. Moyes was applauded after he strode out before the teams entered the pitch to face his detractors.

Patrice Evra
A Patrice Evra goal could not prevent United from crashing out of the Champions League

Bayern Munich - salvation could have emerged in the most unlikely of fixtures for Moyes and United. After a well-fought 1-1 draw in the first leg of their Champions League quarter final, Patrice Evra's thunderbolt put United on the cusp of progression. But a late Bayern rally saw the Bavarians run out 3-1 victors.

Liverpool crushed United 3-0 on their own turf days before City did likewiseGetty

Derby defeats, vol.2 - if the powers that walked the corridors of Old Trafford were thinking of pulling the trigger following the Olympiakos debacle, comprehensive 3-0 defeats against Liverpool and City put Moyes's head on the chopping block in March. United were toothless against their greatest foes and were easily swept aside. The clock was ticking for Moyes.

Moyes Goodison
David Moyes was ridiculed on his return to Goodison ParkGetty

Return to Goodison - the result that sealed Moyes's fate was also one that condemned the club to a season out of the Champions League. Booed as he walked towards the away dugout, Moyes watched on as his United side were out-fought and ultimately out-classed by his resurgent former employers. His ten months in charge came to an end when the axe finally fell two days later.

Ryan Giggs
United legend Ryan Giggs assumed temporary charge of the team's final four league matches

Ryan Giggs appointment - it was left for Ryan Giggs, appointed as interim manager for United's final four league games, to salvage some pride. But even Giggs, the most decorated player in the club's history, was unable to wipe the slate clean entirely after United slumped to yet another home defeat, this time to relegation threatened Sunderland.