Trust counts for so much in football and when you lose Jose Mourinho's, you're toast.

Just ask Mohamed Salah.

The Egyptian is one of a long list of players who have failed to seize the opportunities the Chelsea boss has afforded them and within 12 months he has been sent packing from Stamford Bridge.

It may only be a loan move to Fiorentina, but his appearance against Bradford City in the FA Cup debacle last month is most certainly the last we'll see of Salah in a Chelsea shirt.

Mourinho is a ruthless character. Football may be a team sport, but he is a manager who thinks about one thing: himself.

In some walks of life, that's not a particularly endearing quality. In football, it can mean everything.

Behind the genius of Mourinho the coach is the burning desire for him to set records, to break records and, in the process, write his name into history.

He did it at Porto, at Chelsea, at Inter Milan and in Madrid. Now he's back in west London, he's on course to do it all again.

Without a playing career of any note, Mourinho's needed to use that desire to drive him. It's been his greatest asset at times.

And when a player shows the slightest sign of weakness, he knows he can't have him on board. The danger is too real that his ship will be blown off course.

Mourinho doesn't do freeloaders and in the year he spent at Chelsea, Salah became one.

It's not to suggest the Egyptian isn't a talented player, it's just that he isn't a Mourinho player.

What the Chelsea manager often does is test those around him. He'll put his goalkeepers under pressure to see how they react, for instance, like dropping Thibaut Courtois recently.

How has Courtois responded? By putting in one of his best performances in a Chelsea shirt when the Blues travelled to Parc des Princes to face Paris Saint-Germain last week.

The Belgian's performance in the French capital told us plenty. We already knew he had the ability, but did he have the mettle to cope with Petr Cech breathing down his neck?

Mourinho got his answer.

With Cech hanging around this season, any doubts there may have been over Courtois have been lifted. Whether or not Cech remains a Chelsea player beyond the summer remains to be seen, but without playing frequently, his service has still been considerable to Mourinho this term.

It wasn't about having two world-class goalkeepers; it was about Courtois' acid test.

When the same questions were put to Salah at Chelsea, he never answered them in the way his manager would have liked.

Indeed, he failed to live up to the challenge of competing with Eden Hazard and the rest of that vastly talented attacking midfield core that Chelsea possess.

That said plenty about his character, that when the big moments arrived, Salah couldn't be depended on.

How can Mourinho build for success without knowing his players will deliver? It's quite simple: he can't.

Salah isn't a winner and that's at odds with what Mourinho is attempting to recreate at Chelsea.

If you're of that ilk, you're not worth much to Mourinho, not least the £11 million fee Chelsea paid FC Basel for Salah in January 2014.

It was a gamble for the club and player that has backfired.

Now, in the less intense and scrutinised surroundings of Florence, Salah seems to have got his mojo back. Just don't ever expect it to return to Stamford Bridge.

Garry Hayes is Bleacher Report's lead Chelsea correspondent. All quotes were obtained firsthand unless otherwise noted. Follow him on Twitter @garryhayes