Civil war bubbling in Paris as Ariarne Titmus and Mollie O’Callaghan clash in Olympic 200m | Nicole Jeffery

This will be the nearest that the closeknit Australian swimming team gets to civil war. Two Australian swimmers, alike in talent and ambition, training in the same pool in suburban Brisbane, under the same coach, will go head-to-head for the Olympic gold medal in the 200m freestyle tonight.

For one night only, the détente in which Ariarne Titmus and Mollie O’Callaghan live their lives will be abandoned as they clash for the 200m crown.

Related: Mollie O’Callaghan and Ariarne Titmus aim to get it just right in 200m freestyle showdown | Kieran Pender

Pity Dean Boxall today. The exuberant mastercoach will have to do a juggling act like no other to have both of his champion swimmers primed for a race in which only one can emerge triumphant.

It won’t be anything new for Boxall – he manages the two swimmers daily in his training pool at St Peter’s Lutheran College, mostly by keeping them separate. Titmus trains with the middle distance group, while O’Callaghan works with the sprinters.

But they meet at the 200m distance, the ultimate speed-endurance test.

Titmus will go into the 200m final as the defending champion and world record-holder, having taken that mark from O’Callaghan at the Australian Olympic trials in June. She approaches the 200m with the strength of her 400m-800m training.

O’Callaghan, twice the world 100m freestyle champion, and world 200m champion last year, but competing in an individual event for the first time at the Olympics, will bring her dynamic finishing power and superb underwater skills.

She is known to be a nervous competitor, but winning her first Olympic gold medal in the 4 X 100m freestyle relay on Saturday night, may have quelled some of that anxiety.

Titmus will also be gunning for her second gold in tonight’s 200m freestyle final, after a commanding win in the 400m freestyle. She is now the first Australian woman since Dawn Fraser (100m freestyle, 1956-60-64) to successfully defend an Olympic title.

Both women looked composed as they gave a preview of tonight’s showdown in last night’s semi-finals. At the finish they were separated by just .06sec as they took the top two qualifying spots for the medal race.

Titmus, 23, led for most of their semi-final and touched first to stop the clock in 1:54.64. O’Callaghan, 20, was in fourth for most of the race, but a brilliant underwater turn into the last lap brought her right into the race and demonstrated why she is so dangerous.

O’Callaghan declined to speak after the semi-final, but Titmus was her usual confident self.

“I think once you get into the meet, you get the ball rolling, you kind of start to calm down a little bit and start to feel momentum, so, got the job done tonight and I’m excited for tomorrow,’’ she said.

Earlier O’Callaghan acknowledged the expectation around this race. “There is pressure and there’s expectation. I want to do well for Australia I want to do well for my swim team, I want to do well for everyone and so I’ve got to handle it in a different way,’’ she said.

Boxall will have individual messages for each of his charges before the final, but O’Callaghan gave a hint of what the coach has been telling her, when she said the pressure would be on those ranked No 1 and the past Olympic champions.

“This is my first time having an individual (race) at the Olympics and it’s new and fresh for me, so I’m just going to learn as I go,’’ O’Callaghan said.

Titmus can relax knowing her place in history is secure. With three individual Olympic gold medals she’s already in the pantheon with Fraser, Murray Rose, Shane Gould and Ian Thorpe. If she becomes the first to complete a double-double, she will have a unique place in Australian sporting history.

National head coach Rohan Taylor said only a “handful” of Australian swimmers had been able to “do a Mount Everest climb and then be able to find that same hunger (again) when you are the best and everybody wants to beat you’’.

He agreed that Titmus was “right up there’’ in terms of Australia’s greatest swimmers.

But that doesn’t mean she can’t be beaten. The last time Australia had the top two swimmers in an event at the Olympics was 20 years ago, when world record-holder Libby Trickett and Jodie Henry arrived in Athens for a 100m freestyle showdown. That time it was No 2 Henry who emerged victorious.

Taylor said he was content to leave the management of the two swimmers to Boxall, predicting they would “go about their business’ as usual and “they’ll both want to do their best in the moment.’’

Meanwhile, Olympic rookie Max Giuliani, 21, is planning to make an impact in tonight’s men’s 200m freestyle final, after qualifying for the deciding race in fifth place (1:45.37).

Giuliani, who almost quit swimming to become a tradie only 18 months ago, said he was determined to make the most of this opportunity.Like Titmus, Giuliani is a Tasmanian. He vowed to “get after it’’ in tonight’s final in a bid to grab his first international medal.