Godra. Bigger than Bradman.

Tony Modra hated both the nickname and the description.

But in many ways they sum up the revered AFL figure, who was air-lifted by medical helicopter to a South Australian hospital on Thursday and remained in a critical condition on Friday morning.

Modra suffered undisclosed injuries at his cattle property about 90km south of Adelaide on Thursday afternoon.

In wild weather, it's suggested a fallen tree may have broken through the windshield of the truck he was driving, though police are continuing investigations.

Modra, 57, was flown to a southern Adelaide hospital. News of the accident was met with absolute shock in SA and beyond.

In 1994, at the height of his fame, he wanted to quit the sport. In the lead-up to that season's opening game, Modra missed training.

Coach Cornes sought out his star player and Modra told him: "I'm completely over it. I'm quitting. I don't want to play this game any more; I don't need to go through this."

"The pressure had really got to him," Cornes has recalled.

The coach convinced Modra to play at least one more game. He did. He kicked 13 goals on the AFL's fullback of the century, Carlton's Stephen Silvagni.

Modra continued to play and, in 1997, was a key factor in Adelaide's charge to the premiership but suffered a serious knee injury in the preliminary final - he required a knee reconstruction and missed the Crows' inaugural flag.

As Adelaide's MCG changeroom overflowed with overjoyed players and supporters, Modra sat in an adjoining smaller locker room.

His teammates brought the premiership cup to him and Modra, approached for comment, politely declined with a shake of the head and a smile that somehow appeared simultaneously happy and sad.

In 1998, Modra recovered from his knee injury and played eight games. The Crows again won the flag, but again without their ace attacker: he was infamously dropped by coach Malcolm Blight after the qualifying final.

Modra departed the Crows at the end of that season: he played 118 games and kicked 440 goals for Adelaide.

Modra joined Fremantle, where he booted another 148 goals in 47 matches over three seasons before retiring.

His career featured two All Australian jumpers; three AFL marks of the year (in 1993, 1997 and 2000); the AFL's goal of the year in 1995; and the 1997 Coleman medal as the league's leading goalkicker.

Modra, who was a club leading goalkicker six times - in five consecutive seasons at the Crows from 1993 then at Fremantle in 1999 - was awarded life membership at Adelaide in 2008.