Sir Alex Ferguson has faced many challenges during his time as Manchester United manager, be it Kenny Dalglish's Blackburn, Arsene Wenger's Arsenal or Jose Mourinho's Chelsea.
However, the newest threat - Roberto Mancini's Manchester City - may prove to be the toughest of the lot for Fergie.
Here, Sports Mole looks back at how United have coped with this challenge from their 'noisy neighbours' in a topsy-turvy season.
August
United began the season as they would have loved to finish it - by beating City. A thrilling Community Shield final saw the Red Devils fight back from two goals down to win 3-2.
They began their title defence in style, beating West Brom and Tottenham before a Wayne Rooney hat-trick and Ashley Young brace helped United record a remarkable 8-2 win over Arsenal.
September
United's ominous league form continued through to September with an emphatic 5-0 win over Bolton, in which Rooney scored a second consecutive hat-trick, and a 3-1 win over Chelsea.
A 1-1 draw at Stoke saw United drop their first points of the season, a low point that was accompanied by two draws in their opening two Champions League games.
Fergie's men comfortably progressed into the next round of the Carling Cup, however, easing past fierce rivals Leeds.
October
October saw United pick up maximum points against Norwich and Everton in the league, as well as a hard-fought draw away to arch rivals Liverpool.
Meanwhile, a comfortable win against Otelul Galatai in the Champions League and a 3-0 triumph over Aldershot in the Carling Cup continued the Red Devils' progress in the cup competitions.
However, October also provided arguably the worst moment in Ferguson's 25 years at the club as his side was thrashed 6-1 at Old Trafford by City, United's worst home defeat for 56 years.
November
November brought with it Sir Alex Ferguson's 25th anniversary as United manager, and the Scot was rewarded with an Old Trafford stand being named after him.
Narrow wins over Sunderland and Swansea, as well as a 1-1 draw with high-flying Newcastle, kept the pressure on City at the top of the table, but a draw with Benfica in the Champions League meant that qualification from the group stage would go down to the last game.
United ended the month with a shock defeat to Championship side Crystal Palace in the League Cup quarter-final.
December
United's league form throughout December was, for the most part, faultless, as they won five of their six games, scoring 19 goals in the process.
However, December was the host month of two more shocks to United's season. First, they were dumped out of the Champions League after losing to Swiss minnows FC Basle before bottom-of-the-league Blackburn recorded a fine 3-2 victory at Old Trafford on New Year's Eve.
January
January began as December had finished - with a defeat for United. This time it was at the hands of Newcastle, who ran out 3-0 winners.
The Red Devils responded by dumping City out of the FA Cup, helped by a returning Paul Scholes, before beating Bolton, Arsenal and Stoke in the league.
After getting past one fierce rival in the FA Cup this month, United couldn't get past a second as a late Dirk Kuyt goal saw Fergie's men eliminated by Liverpool.
February
February proved to be a productive month for United as they closed the gap on City as well as progressing in the Europa League.
The month began with Fergie's men fighting back from a 3-0 deficit to draw 3-3 with Chelsea before a 2-1 win over Liverpool that was overshadowed by Luis Suarez refusing to shake Patrice Evra's hand.
A 3-2 aggregate win over Ajax followed this, and the month ended on a high note for United as Ryan Giggs scored an injury-time winner on his 900th appearance for the club to help beat Norwich.
March
March saw Ferguson break yet another record as he surpassed Sir Matt Busby's Old Trafford record by taking charge of his 986th league match, a 3-1 win over Tottenham.
It was also the month that United returned to the summit of the Premier League with wins over West Brom, Wolves and Fulham.
It wasn't all good news in March, however, as the Red Devils were unceremoniously dumped out of the Europa League by Athletic Bilbao.
April
United looked to be marching towards a record 20th league title as they began April by opening up an eight point gap between themselves and City with wins over Blackburn and QPR.
However, a shock 1-0 defeat to Wigan followed and, despite a 4-0 win over Aston Villa in their next game, United wasted a two-goal lead to draw 4-4 with Everton, blowing the title race wide open.
The month ended with one of the biggest games in Premier League history as City hosted United in what many thought would be the title decider. City won thanks to a Vincent Kompany header, putting the Blues back at the top of the table on goal difference.
May
With the title now in City's hands, all United could do was win their remaining games and hope for a slip-up.
Wins against Swansea and Sunderland ensured that United kept their side of the bargain, but it wasn't enough to knock Mancini's men off top spot as Ferguson was forced to settle for second place.
