Martin O'Neill hailed 2002-2003 as Celtic's greatest season since his appointment as manager despite ending it empty-handed.
The Bhoys were beaten in both the League Cup final and the Uefa Cup final before losing the Scottish Premier League to Rangers on the final day of the season.
It was a disappointing end to what has been a great adventure for the Glasgow giants.
But they are not the first side to have suffered such heartache...
Bayer Leverkusen - 2001-2002
When Bayer Leverkusen lost the Champions League final it completed an unwanted treble for the Germans.
There was little shame in losing to Real Madrid and a sublime Zinedine Zidane volley.
But prior to that they had fallen victim to Schalke in the German Cup final and blown a five-point lead in the Bundesliga, two defeats in their final three league games allowing Borussia Dortmund to snatch the title.
It was the fourth time in six years that Leverkusen had finished runners-up - and their trio of near-misses prompted them to be cruelly dubbed "Neverkusen".
Valencia - 2000-2001
Valencia only finished fifth in La Liga in 2001, but they almost became champions of Europe.
Oliver Kahn's saves denied Valencia
The Spaniards knocked out Arsenal and Leeds on the way to the final of the Champions League.
But they threw away a second-minute lead as Bayern Munich won on penalties.
Defeat to the German side meant an unwanted double for Valencia, who had lost in the final a year earlier to Real Madrid.
Spare a thought, too, for Valencia's coach, Hector Cuper.
He had been in charge of the Mallorca side beaten in the final of the 1999 Cup Winners' Cup.
Deportivo - 1993-1994
Deportivo looked like ending the nine-year dominance of Real Madrid and Barcelona in Spain.
They had led the league from the early stages and went into the final game one point ahead and knowing a win would secure their first ever title.
It looked assured when they were awarded a 89th-minute penalty at home to Valencia, but defender Miroslav Djukic missed and they were held to a goalless draw.
That allowed Barca to claim their fourth title in a row, the Catalan club coming from behind to beat Seville 5-2.
Dundee United - 1986-87
For much of the season, Dundee United were fighting it out for honours on four fronts.
Manager Jim McLean had guided his side past Barcelona and Borussia Monchengladbach to become the first Scottish side to reach the final of the Uefa Cup.
And the Terrors were also in contention for the league, the League Cup and the Scottish Cup.
But they eventually finished third in the league and lost 2-1 to Rangers in the League Cup semis.
Defeat to St Mirren in the Scottish Cup final then sandwiched their two-legged Uefa Cup agony against IFK Gothenburg.
Everton - 1985-86
In the mid-1980s, Liverpool and Everton were the dominant sides in English football.
But when Everton beat their city rivals 2-0 at Anfield in February, it looked as though the blue half of Merseryside would be the ones heading for a second straight title and a potential league and cup double.
Liverpool pipped Everton to the double
Then Liverpool responded with a run of 11 wins and a draw from their final 12 games to deprive the Toffees of the league crown.
Everton had their chance to exact some revenge in the FA Cup final, but they threw away a 1-0 half-time lead as Kenny Dalglish's side went on to claim the double.
Leeds - 1969-70
Don Revie's no-nonsense Leeds side were at one stage on course for a league, FA Cup and European Cup treble.
They survived two goalless replays with Manchester United to make the FA Cup final at the third attempt.
The final against Chelsea also ended all square but four days later things began to go downhill when they were knocked out of the European Cup semis by Celtic.
Their league form also suffered through their hectic run-in - and only two wins from their final eight games allowed Everton to clinch the crown.
The FA Cup final replay was Leeds' 63rd game of the season - and they had little left in the tank as they lost to an extra-time winner from the Blues.