New research from the US has found an alarming link between playing football and brain damage, prompting calls for Australia to better study brain injuries in footballers.

The ABC's Four Corners program tonight reveals new evidence about the extent of brain injuries resulting from playing football, with medical experts finding players do not need to have a concussion to cause damage.

The researchers have also started to work with Australian footballers who have suffered serious injuries during tackles.

During his football career, former Auckland Blues half-back Steve Devine - known as Australia's favourite All Black - suffered some big hits, even in his Test debut against England in 2002.

"I remember being in the dressing sheds and talking about moves that we thought would work in the second half and I remember hearing these moves' names and I just had absolutely no idea what they were," he told Four Corners.

The following year in the Super 12 semi-final against the Brumbies, he was knocked out and ended the game on a stretcher.

The injuries kept coming. Devine was knocked out three times in four weeks in the 2006 Super Rugby competition.

He told Four Corners the injuries were taking their toll.

"I'd drive into my garage and I had a hallway, and I was so fatigued I couldn't - I just had to sleep, so I lay down in the hallway and had a sleep and woke up and ... I was a dead man walking really, I had nothing. I was just getting around the field," he said.

US neurologist Professor Bob Cantu from Boston University says a condition has emerged even when players do not experience concussion, called Chronic Traumatic Encephalopathy (CTE).

"These are injuries where the accelerations are not at a level to produce symptoms we recognise as concussion," he said.

"Sub-concussive blows can cumulatively lead to damage to the brain."

Professor of Neurology at Boston University Bob Stern says tests show clear evidence of damaging changes to athletes' brains.

"People who do have a history of repetitive brain trauma as a professional athlete years earlier and who have symptoms now that are consistent with CTE do show changes in their magnetic resonance spectroscopy (MRS)," he said.

"The MRS is showing that there is something wrong, we just don't know enough yet."

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Local research needed

The University of Queensland's Dr Bradley Partridge, who writes about the issue in the Medical Journal of Australia, says urgent research is needed in Australia.

"We don't really have a very good understanding, we don't have these well-controlled studies that would give us the kind of information that we need to know about what precisely is the long-term effect of suffering one, two or more concussions," he said.

AFL player agent Peter Jess has visited Boston and agrees with Dr Partridge.

"We don't have a study on CTE, it's absolutely critical that we have that," he said.

But Royal Melbourne Hospital's Professor Andrew Kaye says there is currently no clear evidence that sub-concussive injuries can cause permanent brain damage.

You can watch the full report on ABC1's Four Corners tonight at 8:30pm.