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"I was hoping at one stage to take a squash ball onto the field because the way he was seeing the ball was like you were bowling with a beach ball," said Morkel (5-146), who finally ended Clarke's latest masterclass at 230 runs early on day two.
South Africa were 333 runs in arrears with eight wickets in hand at stumps.
Clarke's exit marked the first time in two matches and 489 runs he's been out.
The skipper fell just eight runs short of Sachin Tendulkar's mark of most runs scored between dismissals.
His back-to-back double hundreds in Brisbane and now Adelaide put him third on that list, just one run behind Sir Garfield Sobers, who managed 490 from two innings back in 1958.
Since taking over the captaincy last year, Clarke has averaged 72.65 - a better start than any fledgling Australian skipper in history other than Sir Donald Bradman.
Teammate Mike Hussey has played a support role to Clarke at the Gabba and in Adelaide - and for last year's unbeaten triple century at the SCG.
Hussey knows he's got the best seat in the house.
"Geez his stroke play at the moment is just amazing," he said.
"It's just a pleasure to be at the other end and watch it so closely.
"I feel very lucky."