Who knows what would have happened if Sunderland had retained Vito Mannone?

He could have seen his way clear to dropping the ball once or twice, but otherwise there is nothing to dislike about the keeper.

Mannone gave his previous club some great days. His league debut in a 1-0 win over Manchester City, the Great Escape of 2013-14, the 3-0 win at Newcastle and the run to Wembley in the same season are all to be cherished.

Less fondly remembered are his role in the annihilation at Southampton in October 2014 and the almighty clanger he dropped against Arsenal a week later.

He is a good, but not great goalkeeper.

However, you would need to be a picnic short of a picnic not to think he isn’t an arm and a leg better than anyone seen between Sunderland’s posts this season.

When he left for Reading last July, it elicited little comment among the fans, who wished him well and didn’t mind just as long as his replacement was at least as good.

But Mannone’s departure was more pivotal than anyone realised at the time.

Not that SAFC’s bewilderingly immodest CEO Martin Bain has admitted that selling him was a significant mistake. Quite the opposite.

Last September, by which time everyone had taken a good look at Jason Steele and Robbin Ruiter, Mr Bain was buoyant about the “efficiency” of the club’s transfer dealings last summer.

He told the Echo then: “I look at the transfer window as a success.

“Leave the finances aside for a second, we sat down and we said, right, what kind of footballer do we want to bring to the club?”

He added, perhaps regrettably: “Vito Mannone goes back to this case in point about how we’re trying to run the club. Vito is obviously a very good goalkeeper.He had a year left on his contract, which was going to run down and Sunderland would have got nothing for him.

“The right thing was, and this is regardless of the other circumstances, to ensure that the club protected its investment and got some money for Vito. That’s what I mean about efficiency.”

How efficient?

Sunderland received around £2m for Mannone; the same as they paid Arsenal for the player four years earlier. So no profit there.

He did have just a year left on his contract. So was any attempt made to extend it?

Jason Steele was brought in for £500,000 and given a four-year contract. It seems unlikely that he will be sold at a profit; or indeed at all as his queue of admirers is a short one.

But the financial repercussions are far more serious than that.

Steele was signed from Blackburn Rovers, a relegated side who eventually dropped him for their final five games of last season (when they kept three clean sheets).

I don’t wish to be unkind, but Steele, Ruiter and Lee Camp have between them made bad errors in virtually every Sunderland game of 2017-18.

We will never know what difference the retention of Vito Mannone would have made.

But we have to wonder if there would be the current six points distance from safety had there been a smaller pile of goalkeeping howlers to remember this season by.

Two million quid for Mannone, but relegation to the third tier as a consequence?

This may be an overstatement and an over-simplification.

Nevertheless, it’s somewhat difficult to spot the “efficiency.”