Has Wolff seen more trouble brewing?

At what point does controversy within a team overstep the mark?

Mercedes motorsport boss Toto Wolff's remarks of late about his two star drivers have raised just such a question.

Come the end of what appeared to be a far less contentious Formula 1 season than in 2014, one that certainly appeared from the outside far easier to manage, Wolff dropped a blunt reminder to Lewis Hamilton and Nico Rosberg.

On two separate occasions Wolff has made clear if the occasionally fractious duo do not keep a lid on their animosity towards one another, and it affects the team as a whole, then one or the other will be shown the door.

That Wolff felt the need to go public with his comments is a surprise in itself as normally these admonitions are voiced behind closed doors.

In 2014 it was not until Rosberg felt the need to collide with Hamilton in the Belgian Grand Prix that Wolff openly said enough was enough.

Rosberg decides enough is enough at Spa last year © LAT

That was the culmination of a tit-for-tat campaign as one driver attempted to out-do the other and, with the title very much on the line, Rosberg took matters into his own hands and paid the price.

Rosberg wasn't the same driver after being internally disciplined, and a fired-up Hamilton thoroughly dominated the remainder of the season to claim his second crown.

For the majority of this season the pair pretty much behaved themselves on track, with barely a wheel out of place, and little for Wolff to get worked up over.

Then came the Japanese GP, where Hamilton took full advantage of an opportunity to get his elbows out as they went wheel-to-wheel through the opening corners. Rosberg was edged off track in what transpired to be a race-deciding move.

A fortnight later heading into the opening corner of the United States Grand Prix, we had a repeat as Hamilton again showed Rosberg who was boss by running the German wide, dropping him from first to fifth in one fell swoop.

The conditions that day played a part in Rosberg's sterling recovery drive, only for a mistake late on to prove decisive as it cost him the win and the title.

Rosberg's disgust with himself, and with Hamilton for the Turn 1 incident, were apparent with the cap-flinging incident ahead of the podium ceremony. His suggestion that Hamilton had gone "one big step too far" reopened all the old wounds.

Wolff has felt moved to threaten repercussions before things escalate © XPB

The inference from Wolff's comments is that the acrimony between the two has intensified, off track and away from the public eye, and is starting to drive a wedge through the team.

A couple of robust moves from Hamilton, a tossed cap and a few choice words between the pair hardly seems cause for Wolff to all of a sudden air the kind of thoughts he has of late. There is clearly more going on within the confines of the Mercedes garage than the wider world has seen.

Hamilton underlined the 'no love lost' feeling between him and Rosberg that exists these days when he stated that for as long as the two of them remain rivals in Formula 1 - whether in the same team or not - they will never be friends.

Explaining the relationship to Autosport, Hamilton said: "Nico has his group of friends, I have my group of friends.

"We don't do dinner together, we don't want to party together, we don't want to go to the movies together, we don't want to hang out.

"We're fierce competitors, and ultimately he wants to beat me and I want to beat him.

The friendly selfie count diminished as the season progressed © XPB

"I'm sure one day when we retire we'll sit back and laugh about all this shit that has happened and all the competitiveness.

"We'll be chilling, our kids will be playing together and all that crap, but right now we're not there, and there's no need to be."

If ever there were five sentences that highlighted the breakdown of what was a fairly relaxed team-mate relationship - between two childhood friends, no less - when Hamilton arrived at the start of 2013, then they are it.

F1 history has proved team-mates do not have to get along, but it helps - as Wolff alludes.

The disdain can become too much for the team as a whole to bear, and it leads to internal relationships breaking down, which will eventually impact on the performances on track.

Wolff is undoubtedly attempting to avoid such a scenario arising, to nip it in the bud before it gets out of hand. He sees something going on that could get out of control unless handled now. And that requires threatening the ultimate sanction of showing someone the door.

As Wolff explained, the rivalry between Hamilton and Rosberg is "very competitive and very fierce, [and] it is important to contain that and make sure it doesn't spill into the team, and it doesn't cause controversy within the garage.

The opening lap at Suzuka was one of the 2015 flashpoints © XPB

"The spirit within the team is essential. It is one of the forces which makes us who we are and what we are, and if there is animosity within the team, that would be detrimental.

"I said if we were unable to contain that fierce competition and if it were to spill over into the team then we would need to look at how we set up the driver line-up for the future."

The flipside is Wolff also recognises for the sake of Formula 1 as a whole, given the dominance of his team is detrimental to the show, it is crucial for Hamilton and Rosberg to be at odds with one another.

There is nothing like a good intra-team feud to keep an audience interested.

As Wolff added: "We love the competition on track and we think that controversy and the racing needs to be hard."

So when does that controversy go too far?

Hamilton and Rosberg do not like one another, that much is clear, and they've already committed F1's cardinal sin of one deliberately running into the other - or at least not doing their utmost to avoid doing so. What will it take for it to spill over? A punch up?

It's hard to imagine Hamilton/Rosberg angst reaching Senna/Prost levels © LAT

At the end of the day this is not Prost/Senna we are talking about. It would be a huge shock if Hamilton/Rosberg animosity reached those legendary levels.

On the face of it there is an easy opt out. Hamilton has three years remaining on a new contract that was signed in May, Rosberg only one. If Mercedes decides someone needs to go, one exit would be much more straightforward than the other.

Perhaps Mercedes will bide its time with Rosberg before settling down to talk over a potential fresh deal, waiting to see how the early exchanges of 2016 unfold first.

Hamilton remarked at Mercedes' celebratory end-of-season Stars & Cars event recently there are no issues with Rosberg.

From a platform as a three-time Formula 1 world champion, and ahead of a laidback Mercedes jamboree, that is easy to say.

But once battle commences in 2016 then the current still waters of their partnership will be tested again, in a situation where Hamilton has the boost of two straight titles, but Rosberg has momentum from his excellent end to 2015 and the pressure of having to earn a new deal.

Those circumstances seem ripe for sparking further controversy and some tough decisions for Mercedes.