The Peter Snowden-trained Long John moved to second favourite for the Caulfield Guineas with a dominant victory at Flemington on Saturday.
Long John lost his unbeaten record with a first-up third at Moonee Valley to Cauthen two weeks ago but got back to winning ways as he strode clear in the Listed Henry Bucks Stakes (1400m) to win by 2-1/2 lengths.
New Zealand colt Cauthen, the $3.50 favourite, pressed forward from a wide gate to be second in the run but never quickened in the straight, finishing 12th.
Any examination of Cauthen showed the horse was suffering from a case of the thumps, a veterinary term for irregular diaphragm spasms.
Cauthen's trainer Andrew Campbell was a dejected figure in the mounting yard.
"Racing's a great leveller," he said.
From a good barrier Steven Arnold settled Long John ($5) just off the speed.
He hit the front 300m from home and strode away to defeat the Peter Moody-trained Weinholt ($21) while another Snowden-trained runner, San Diego ($81) finished another long neck away third.
Long John was $16 in the TAB's Caulfield Guineas market but moved to $5 behind Prince Harada ($4.20).
Cauthen drifted from $6 to $18.
Darley's Melbourne stable foreman Paul Snowden said Long John had improved significantly from his first-up run.
"A lot was going to be learned after today but obviously he's put paid to them pretty good," Snowden said.
Snowden said Long John would head to the Bill Stutt Stakes or Caulfield Guineas Prelude next with the Darley team to decide if he presses on to the Caulfield Guineas.