The fear of what ifs.
What if he didn't get up; what if his skull was fractured; what if this was to be his last experience of cricket; what if, what if.
As it happened, the batsman sat on the pitch several seconds rubbing the side of his head, gave a rueful "I'm okay" and carried on batting.
No idea how he was the following day, or week, or month. Did he have recurring headaches, or worse? Did the experience turn him to tennis, or swimming?
And so this mind has spared many thoughts for Sean Abbott this week. The first thing he should do is avoid the thoughts of others on his cricket future.
Some former players have opined that he'll never play again, or that he'll need counselling, or that he simply needs to put the moment out of his mind and get back into it. Far easier said than done.
The only person who knows how and what Abbott is feeling, is the young man himself.
At 22, and with one ODI and three T20 internationals behind him, Abbott, who hails from Windsor about 60km north-west of Sydney, will be numb. No amount of "you did nothing wrong" will help him.
There's talk of whether the bouncer should be outlawed; helmets should be reinforced (Answers: no, and if it helps, of course)
Think of the number of balls delivered every day around the world. Then think of the number of batsmen struck by the ball. Then think of the number who suffer serious injury.
That leads to the obvious conclusion that what happened to Hughes was not only a freak moment but a desperately sad confluence of events: a bouncer, a mistimed shot, the spot the ball struck.
Here's another what if: Hughes times his pull shot to perfection, the ball rattles into the fence at the Sydney Cricket Ground. Hughes moves to 67, pressing on towards a century in his bid to regain his Australian test spot for the Indian series.
Abbott completes his 10th over, instead of forever being locked on 9.3 overs.
What sort of batsman was Hughes? A dasher, with extravagant shotmaking ability. He smeared New Zealand around the Basin Reserve one day in 2010, making an unbeaten 86 out of 106 for none, setting up a 10-wicket win for Australia.
Hughes struck the ball to unusual places. He was never dull.
He was also a fighter. His was not a career loaded only with highs, like the twin centuries in his second test against South Africa at Durban, the youngest player to achieve the feat.
Against New Zealand in late 2011 he was dismissed, quirkily, in identical fashion in all four innings: c Guptill b C. Martin at either second or third slip.
He'd been gone from the test team for 16 months. The word was he was close to a recall. His best years lay ahead.
So it should be for Abbott. Whether it will be, only he knows. And right now is not the best time to be making decisions on that.
You'd hope that was not the last ball he bowls in cricket. But consider this: in future whenever he turns at the top of his mark and thinks "bouncer" what will be uppermost in his mind?
