After an off-colour showing at the Athens Games, Australian backstroker Matt Welsh is ready to reveal his true form at this week's world short course swimming titles at Indianapolis.

The Sydney Olympic triple medallist revealed a virus had severely hampered his Athens campaign - much to his relief.

Welsh, 27, said he was comforted by the revelation but did not use it as an excuse.

"To find out that I had been suffering a virus at least gives me an answer," said Welsh.

"I would not change the way I raced and in fact I'm even prouder of the way I was able to race under those circumstances."

Welsh struggled at Athens, finishing fifth in the 100m backstroke despite leading past the 50m mark.

After detecting the virus upon his arrival in hometown Melbourne, Welsh went on to win a record sixth national short course backstroke treble - taking his total of Australian championships over the last six years to 20.

Buoyed by his national success, the Victorian said the "real Matt Welsh" would shine in the 30-strong Australian swimming team at the world short course titles which start on Friday morning (AEST).

The defending 100m backstroke world short course champion will go head-to-head with dual US Olympic champion Aaron Peirsol in the 50m, 100m and 200m backstroke events - starting with the 100m showdown on the opening day.

Welsh is not only wary of Peirsol at the world titles.

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