If the timing and the circumstances of Martin O'Neill's dismissal as Sunderland manager were a shock, the realisation that Paolo Di Canio is to be his successor trumps it.

If O'Neill represents tried and trusted, then Di Canio, who has 18 months' experience in Leagues Two and One with Swindon Town, represents untried and untested, certainly in Premier League terms.

Now the controversial 44 year-old Italian will be thrust into a relegation scrap which Sunderland look less prepared to cope with successfully than Wigan Athletic directly below them or Newcastle United directly above them.

At least Aston Villa lost yesterday, leaving Paul Lambert's team third-bottom, but if QPR were to win at Fulham tonight, the high anxiety on Wearside would only increase.

Yet placing an inflammable character such as Di Canio into this situation is like striking a match quite close to a toxic environment. If Di Canio takes charge until the end of the season only, or beyond that regardless of Sunderland's May destination, his first game will be at Chelsea and his second at Newcastle United.

Those are venues for controlled aggression and last season in O'Neill's seventh match in charge Sunderland lost 1-0 at Stamford Bridge and then led 1-0 at St. James' Park until injury-time.

Elsewhere last season Di Canio was sent to the stands during the Swindon-Oxford local derby.

A reputation for high-energy motivation, on the touchline and the dressing room, is what O'Neill brought. This sounds quite like Di Canio. The one-time Mussolini supporter turned eco-pagan does not lack colour.

But what O'Neill also brought was under-appreciated nous and experience. Last week he was asked if he had ever been in a relegation battle before and he replied: "Yes, last season." It was a reminder to the forgetful that Sunderland were falling out of the Premier League when he arrived. He helped save them and deserves credit for that.

True, Sunderland have not galloped on as forecast by some this season and there is an argument that while the club and O'Neill continued to recruit players from Britain, the value and quality in the market has moved abroad, as demonstrated by Newcastle and Swansea for example. This is exacerbated by the size of the fees paid for Steven Fletcher and Adam Johnson.

But the fact is that this could not yet be called O'Neill's team. Ten of the 14 who played some part against Manchester United on Saturday pre-dated O'Neill at the Stadium of Light and that is 16 months on from him replacing Steve Bruce.

Also true is that on his unveiling, after a hiatus from the game, O'Neill had spoken of Barcelona's style and how it was invigorating football. Such style never materialised on Wearside; there was an initial explosion of energy that catapulted Sunderland away from relegation but too often the formation and methods were predictable.

O'Neill's response to this kind of criticism would be: have you seen these players?

To view it like this, however, is to apply logic. This may be misplaced because the human factor is always under-rated.

We do not know the nature and frequency of the conversations O'Neill had with Sunderland's chairman- owner Ellis Short - it was said yesterday that the sacking was made by telephone. What we do know is that a man of O'Neill's stature and pride is unlikely to wish to bend the knee. In that regard, there may be some comparison with his end at Villa with Randy Lerner.

In recent weeks there is thought to have been greater distance and tension between the two key figures and with Niall Quinn no longer there to massage friction, the 32 year-old Margaret Byrne, from near Newry, has increased responsibility.

Ultimately, though, these decisions are the will of Short, a venture capitalist billionaire who, one imagines, usually has the final say.

As such the potential appointment of Di Canio may not reward a search for logic. Who knows if Short and Di Canio move in the same circle? It helped Alan Pardew at Newcastle, and Joe Kinnear before him.

But if Sunderland dismissed Martin O'Neill because of the methods he was using, rather than because his and Short's personal relationship deteriorated, then they will have to convince their fanbase that Paolo Di Canio has a different approach. They will need to convince that they know the scale of Di Canio's achievement at Swindon Town, where he won League Two, its context in terms of opponents'

strength on the pitch and economically. It has to justify itself at a sporting level.

This will be Sunderland's fifth manager in the five years since Short bought a chunk of the club then controlled by the Drumaville consortium. The search for success and stability goes on.