That's the view of former F1 driver and reigning World Endurance Car champion, Allan McNish, who believes it's no surprise the pair aren't friends, but cautions against the situation getting any worse as the championship heads to North America for this weekend's Canadian Grand Prix.
Mercedes, Hamilton and Rosberg have been the stand-out performers in 2014, with victory in all six races, totally dominating the rest of the field, the Brackley-based squad has amassed 241 points already, 140 ahead of nearest rivals Red Bull, whose world title memories of the past few years are fast disappearing.
However, it is the rivalry between the Mercedes drivers that has the potential to derail all the good work achieved so far.
Rosberg's controversial qualifying accident in Monaco put greater strain on a relationship that was already fracturing following Hamilton's claim that he had greater hunger for the world title because of his impoverished upbringing, compared to his teammate's luxury lifestyle in Monaco. A few weeks before that in Spain, Hamilton had said he wanted to mentally 'break' Rosberg. When the German was told that on BBC TV he looked somewhat bemused.
It's clear that Rosberg is the one who thought the pair were friends and had been for many years but Hamilton clarified after Monaco "we are not friends, we are colleagues". More conciliatory words have been forthcoming since then but that may be more of an effort from Mercedes to present a united front. However, McNish believes the team has to do much more than a simple PR exercise.
"It's not just [that], the team has to control it, they have to get on top of the situation, they can't let it be destructive to their world championship campaign," he told The Huffington Post UK. "Mercedes have got everything at their feet this year, they can't let it be destructive."
The three-time Le Mans winner, who now commentates on F1 for the BBC as well as acting as a brand ambassador for Audi, is not surprised at the tension that has developed in the Mercedes camp though.
"I don't think you can ever be best of friends in a competitive environment when you are fighting for a world championship - bluntly.
"It's not abnormal to have situations flare up in these positions because at the end of the day one of them is going to be world champion and the other one is not. So, it's not a surprise to me that their friendship is not a friendship... It's a working relationship. Each one has to beat the other to be world champion and he will do everything he can to do that and he should. If he doesn't, then he doesn't deserve to be world champion."
McNish agrees that there has been some calming of the situation since Monaco both inside the team and in the media coverage, but believes that doesn't hide the fact that the pair are still fighting an intense personal battle.
"You respect your teammate as a competitor but it's impossible in a cutthroat business where there can only be one winner for there to be total and utter openness and friendship in it. Twenty years after they've retired, possibly, but not on the day."
In his latest post on his personal website, Hamilton made little reference to Monaco, saying only that the weekend was "not what I was aiming for". Instead he looked forward to Canada, where he has won twice, and to racing at a circuit that is one of the highlights of his F1 year.
"Montreal is one of my favourite weekends of the year," he wrote. "It's where I won my first Grand Prix back in 2007 and I've had another two victories there since, so it holds some special memories for me. The circuit is one which forces you to be very aggressive and that suits my style!"
McNish agrees that the Circuit Gilles Villeneuve suits the 2008 world champion but believes it is still too close a call to make about who will be standing on the top step of the podium on Sunday afternoon.
"It's a circuit where Lewis has gone well at in the past and one that tends to suit his driving style pretty well. It's very tight. If you look at the stats, they've been separated by less than a tenth of a second in most sessions this year.
"I don't see the ruckuses of what happened in Monaco but I think Canada is going to be a very intriguing weekend to see which way that pendulum swings.
"It will be a pretty titanic fight."Suggest a correction