OPINION:Once again, we have a former great player discovering that the switch to management is anything but smooth, writes Mark Lawrenson

YESTERDAY'S NEWS from Sunderland didn't come as any great surprise; once Roy Keane talked publicly about his self-doubts, about how he wondered if he had the ability to be a manager, that, for me, signalled the end of his time at the club.

So, once again, we have an example of a former great player discovering that the switch to management is anything but smooth, and while Keane began his reign at Sunderland in spectacular style, taking them from the bottom of the Championship to promotion as champions, this season has been nothing but frustration.

Sunderland are third from bottom of the table, immediately below them are Blackburn, managed by another top-class former player, Keane's midfield partner at Manchester United, Paul Ince.

Like Keane, I'm sure, Ince must have believed his years playing at the highest level, for club and country, would stand to him and make success in management in the upper reaches of English football more than achievable. He might get there yet, but he is under severe pressure.

Other former Alex Ferguson players - among them Mark Hughes, Steve Bruce and Gordon Strachan - are enjoying happier times in management, but there has been a trend over the years where some of the greatest players just couldn't cut it as managers. Bobby Charlton is probably the most quoted example.

Look at the big four clubs in the Premier League, Manchester United, Chelsea, Liverpool and Arsenal, all managed by people who had modest playing careers: Ferguson, Luiz Felipe Scolari, Rafa Benitez and Arsene Wenger. Add Jose Mourinho, as just another example, to that list.

There are endless theories about why this is, perhaps the most popular being that a former great player struggles to deal with or understand lesser players, fails to comprehend how they can lack the abilities and instincts they took for granted in their playing days.

It's fine if you have the resources to go out and buy a squad-full of the best of international players. But if you don't, if you have to use your judgment, if you have to pick out players with real potential, often from the lower leagues or your youth set-up, that's where the real challenge lies. To spot talent, and the right mentality, and to be able to nurture and develop it: the ability to do that is what makes the great managers.

And that, for me, is the most important skill in management: judgment of players. I believe Keane was doing a decent job at Sunderland, and I remain convinced they will avoid relegation, but there is no doubt his judgment was lacking when it came to signing players.

Too many of the people he brought to Sunderland just weren't good enough, Championship players at best. He, evidently, believed they had the ability to become Premier League players, with his guidance. But in most cases it just didn't happen. That was a lack of judgment.

And there was a lack of patience, too. That Keane used 27 players this season - in just 18 league and cup games - more than any other Premier League side, showed an impatience, and a constant scrambling to find his best side.

In some senses that confirmed what many said, when he took the job, would be his weakness: an inability to deal with or have patience with players who simply do not have the ability or drive he possessed in his playing days.

So, yes, that persistent chopping and changing suggested frustration and impatience on Keane's part. The talk was he would often choose players based on their performance in training that week, when you really should be just picking the best players you have at your disposal, regardless of how fired up they were in the last training session.

Perhaps because of their limitations as players, Ferguson, Wenger and the rest have a greater ability to get the best out of the weakest links in their teams - and, after all, every team is only as strong as its weakest link. Sunderland, despite the money spent, just have too many weak links.

More than anything, though, playing football and managing a team are just two utterly different disciplines, as I learnt from my own brief time as a manager. They are worlds apart, and because of that there really is no logical reason to believe a great player should become a great manager. Some do, but most don't.

As for Keane, I would be surprised to see him ever return to management. He's tried it, I don't think he enjoyed it, certainly not this season. He doesn't need management, he has more than enough money, so he can afford to walk away. I think he'll do other things with his life now.

He'll be missed, especially by the media - in some ways, for them, he was like Mourinho, but without the burning desire or need to succeed in management.

As for Triggs, he'll get so many walks he should be fit for the 2012 Olympics.