The frontrunner in the race for the Republican presidential nomination Donald Trump has gone after the NFL and American Football saying the game, like the country itself, "has become soft". As has become hallmark for Trump, the comments courted controversy given the concussions and other serious, sometimes life-threatening injuries which have become common in the modern game.

"Football has become soft. Football has become soft. Now, I'll be criticized for that. They'll say, 'Oh, isn't that terrible.' But football has become soft like our country has become soft," the conservative property Tycoon told a crowd of 2,000 at rally in Reno, Nevada, on 10 January.

His comment has been criticised, not least of all for its timing, as two players were knocked unconscious during separate NFL matches over the weekend. Nevertheless, the frequent injuries in the sport did not stop Trump from waxing lyrical on how American Football, like the US, needed to be great again. Hitting on a key theme in his campaign, Trump harked back to the erstwhile glory days of the US.

Republican Presidential candidate Donald Trump
U.S. Republican Presidential candidate Donald Trump speaks at a rally in Reno, Nevada January 10, 2016Reuters

Analysts and pundits claim Trump's meteoric rise to the front of the GOP race comes as a result of the reality star's ability to speak to the disenfranchised 'little guy'. His supporters refer to themselves as "the silent majority".

"It's become weak, and you know what? It's going to affect the NFL. I don't even watch it as much anymore. It's going to affect the NFL. I don't watch it. The referees, they want to all throw flags so their wives see them at home," Trump told his supporters to laughter.

While Trump has led national polls against his rivals for weeks, in conservative Iowa the hotel magnate trails junior senator from Texas Ted Cruise by four points, according to an NBC poll.

Trump has come out on the offensive against Cruz, attacking his eligibility to run in the race because he was born in Canada. Trump was famously active in the 'birther' movement against Barack Obama which claimed he too was not a naturally born US citizen and therefore could not be president.