The prolific New South Wales left-hander was stung by criticism last year from former chief selector Trevor Hohns that fielding was a key factor in his original omission from the South African touring party last season.
He was later flown in at the 11th hour for a one-day international against South Africa in Cape Town, dismissed for a jet-lagged duck, then sent back to Australia.
The 27-year-old, who carries a British passport, played in two Test matches against South Africa at home last summer after weighing in with 24 first-class centuries in six years.
But Hohns' criticism spurred Jaques to shed weight in the off-season.
"If you lose a couple of kilos you're going to be more agile and hopefully that will translate into fielding and running between the wickets," he told reporters Friday. "I'm feeling really fit."
Jaques said his personal experiences from the past 12 months would stand him in good stead should another national call-up come this season.
After registering a record four domestic one-day centuries in one season (2005-06) then scoring 94 on debut with the Australian limited-overs side, Jaques was propelled from a position of relative anonymity into the national consciousness.
"It was a massive eye-opener," he said. "I feel like I learned a lot from last year about what I need to do to stay up.
"I was ecstatic to be picked for Australia. It wasn't always ideal preparation, flying halfway around the world, getting a couple hours' sleep and playing jet-lagged, but that happens in professional sport. You've got to do the best you can."