COMMENT: So who's going to make this call? Better yet, who should be making this call? Ralf Rangnick has lost not one, but two more of his coaching staff this week. And the identity of any replacement could offer us more about the German's position at Old Trafford long-term...

For the moment. As it stands. Rangnick will depart at season's end. At least, that's what's on paper. But as things fall into place around him, the idea of the German 'doing an Ole' and turning this caretaker post into something longer term cannot be discounted.

For now, we're seeing a transformation at Carrington. The youthful, inexperienced staff of Ole Gunnar Solskjaer are making way for the battle-hardened Rangnick and his men. It's a contrast and there's no doubt the players are feeling it.

The 35 year-old Kieran McKenna has just left to take charge of League OneIpswich Town, taking with him Martyn Pert. United's former strength and conditioning coach jumping at the chance to work as McKenna's No2. Pert's departure, while under-reported, cannot be underestimated given he's fluent in Portuguese.

Of course, before last week's double departure, Michael Carrick, 40, also walked out. Rangnick made an attempt to convince the Geordie to stay, but he couldn't be persuaded. Like McKenna, Carrick was a Jose Mourinho appointment. United's former manager declaring the decision at the time was made with the future of the club at heart. It was to be expected both men would develop and grow as coaches under Mourinho. The Portuguese promoting the pair to replace his long time assistant Rui Faria: "When Rui is leaving after 17 years I have nobody, nobody in the world of football ready to be my assistant manager. Nobody.

"So I prefer to educate people, to structure my staff in a way where there is space for their education, for their improvement."

Now both are gone. As is Solskjaer. And United's players have found in their place a 63 year-old manager, a 49 year-old assistant in Chris Armas. Plus for many, for the first time a shrink. Let's say, a 'mental coach'. At 46, Sascha Lense has been in the trade for seven years. And - at least perhaps - it's significant Rangnick introduced Lense by highlighting that he was a decent footballer during his playing days. Like Armas, Lense has found a way to stay involved in the game after a lengthy playing career.

All gone? From left - Carrick, Solskjaer, McKenna and Phelan

So they have miles in their legs. Years on the clock. A playing career to point to. Again, it's a contrast to those whom previously worked day-to-day with the senior squad at Carrington.

And then there's Helmut Gross. Now 72, retired and living in England. Gross has made himself available to Rangnick. For the moment, he'll be an advisor. A sounding board. But we could also see the inventor of the gegenpresse on the Carrington training pitches this season.

A conscious move of extremes? Perhaps. No matter the futures of Carrick and McKenna, Rangnick always planned to bring in his own, experienced No2. Just as he planned to add Lense to his staff and rope in Gross to go around one more time. But now, with McKenna's departure, you fancy another appointment will need to be made.

The Ulsterman was conspicuous in Rangnick's first weeks. During games the pair were seen regularly exchanging views. While Mike Phelan appeared to lose his seat in the United dugout, Rangnick had McKenna stick close to him. There was a relationship developing there. But now McKenna is gone.

And with him goes three years of Premier League coaching experience. Suddenly, Rangnick and Armas are in a new country, in a new competition and on their own. At least unless Phelan is called back from the cold.

There may've been player complaints about their inexperience. Doubts about their training methods. But leaving with Carrick and McKenna is all that local know-how. As experienced as Rangnick and Armas are, this is their first time involved in English football. Indeed, this is the first time Armas has competed at any level in Europe. The prospect of being a steady pair of hands and working their way through a gradual transition has been ripped away. The German and the American, for the moment, are fending for themselves.

So you do fancy a new coaching appointment will soon be made. One with Premier League experience? One with a United connection? Or will the choice be more a reflection of Rangnick's methods? Another with a link to the German? It'll be fascinating watching which way the club goes. And it could tell us a lot about how open that door is to handing Rangnick longer than his current deal to June.

For the moment, it does appear United will move to appoint from outside. The club's academy, where McKenna was plucked from, have again undergone major changes this season. Though an outside bet could be U23s assistant coach Neil Ryan. Given his extensive playing background in the US, there could be some synergy between Ryan and Armas.

But there's more to consider for Rangnick and his higher ups than simply a past playing cv. Will the appointment be made with an eye for the future? Will it be done as a stop-gap? Will it be Rangnick's call, as Armas and Lense have been, or a decision made by technical chiefs John Murtough and Darren Fletcher?

There's a lot to go into this appointment and there'll be a lot to be read from it. Whomever is to sit alongside Rangnick and Armas in the United dugout could offer us more about the German's position at Old Trafford long-term...