By IAIN STRACHAN
Having failed to produce for the first time in a previously unblemished managerial career, Martin O'Neill will be under pressure to get it right in his next job or risk blowing the chance of a gig at one of the heavyweight clubs.
O'Neill was sacked by Sunderland on Saturday after eight games without a win - a run which has left the team 16th on the English Premier League table, just one point clear of the relegation zone.
With Paolo Di Canio now in his place, the Northern Irishman - not to mention the club's fans and owner, Ellis Short - must be wondering how it came to this.
Having taken over from Steve Bruce in December 2011, O'Neill produced instant results at the Stadium of Light, inspiring the players to seven wins from his first 11 league matches in charge.
Safe from the threat of relegation, a potential push for the Europa League stalled and their 2011-12 campaign tailed off - a familiar sight and no cause for alarm among fans of the Wearside club.
A full pre-season under O'Neill and the European summer transfer window to strengthen a respectable squad was expected to make all the difference, with a top-10 finish the minimum expectation this term.
There was no shortage of money to spend, either.
Eyebrows were raised when Steven Fletcher was prised from relegated Wolves for the princely sum of £12 million, joined by Adam Johnson from Manchester City for a reported fee of £10 million.
Carlos Cuellar, an O'Neill favourite at Aston Villa but underwhelming in recent seasons, and injury-prone veteran Louis Saha signed on free transfers.
Out the door went Michael Turner, Kieran Richardson and George McCartney, while Asamoah Gyan's transfer to Al Ain was finalised after he spent the majority of 2011-12 on loan at the UAE Pro-League side, having been lured away by the offer of massive wages.
But having been given both the time and money to refurbish his squad, O'Neill's Sunderland failed to set the world alight in the first half of the season.
Sunderland have swapped one animated touchline character in O'Neill for another in Di Canio [pictured].
Cue the January transfer window and more questionable business. The sale of Fraizer Campbell to Cardiff, little remarked upon at the time owing to the striker's poor return in front of goal, was thrown into sharp relief when Fletcher was ruled out for the rest of season through injury.
Arriving in January were Scottish veteran James McFadden and Swansea centre-forward Danny Graham.
The pursuit and eventual £5 million capture of confirmed Newcastle United fan Graham was a curious affair. Prolific with Carlisle and Watford but competent at best for Swansea, Sunderland must now rely on the 27-year-old journeyman for the goals that will keep them in the top flight. He is yet to find the back of net in the league since joining.
With the starting XI hardly world-beaters, Sunderland's lack of depth and viable alternatives reflects poorly on O'Neill, but it is now Di Canio's problem to fix.
The decorated former Nottingham Forest player must now concern himself with how to revive his flagging reputation as a safe pair of hands in the dugout.
Not so long ago, it appeared as if the only way was up for the energetic Ulsterman.
Having served his apprenticeship to great acclaim at Wycombe Wanderers, O'Neill - a brief, abortive stint at Norwich aside - went from strength to strength.
There was promotion to the Premier League and an unexpected League Cup triumph with Leicester City, followed by three Scottish Premier League titles and an appearance in the UEFA Cup final with Celtic.
At Aston Villa, O'Neill secured three successive sixth-place finishes and took the team to the League Cup final in 2010, before jumping ship, somewhat acrimoniously, when owner Randy Lerner made it clear the manager's resources would soon be drying up.
As a precursor to challenging for a role at a top-four club, fulfilling the potential of sleeping giant Sunderland appeared to be the ideal project for O'Neill, and his first months in the job promised much, only to end ignominiously.
Now the next move is crucial. It is easy to forget, with his lively touchline antics and head of wiry black hair, the one-time rising star of British management is no longer a young man.
At 61, he is just two years younger than Arsene Wenger and only a decade shy of Sir Alex Ferguson, the man he was once - like so many others before and since - tipped to succeed at Old Trafford.
That prospect now appears increasingly unlikely, and a significant success story will need to emerge from his next posting for O'Neill to again be considered worthy of a spot at the top table.