Newly appointed Twenty20 captain Mitchell Marsh aims to keep Australia "nice and relaxed" as they pursue an unprecedented triple crown of titles across all formats at the World Cup.

The laid-back all-rounder leads a seasoned 15-man squad in the June tournament, aiming to rectify their failure to reach the knockout stages in the 2022 home event.

Marsh's appointment as skipper this month, succeeding the retired Aaron Finch, marks a remarkable turnaround from being one of Australia's most criticised players to one of its most respected. Initially seen as a future star, Marsh debuted internationally at 19 in 2011 and was named Test vice captain after the 2018 ball-tampering scandal. However, he was later dropped from all formats and lost his national contract due to poor performance.

Now back in favour, chief selector George Bailey believes Marsh can inspire Australia to emulate their success as current one-day and Test world champions. Pat Cummins, who achieved these titles, remains in the squad but stepped down from the captaincy.

"I think he's just got the natural characteristics of someone who is very genuine and shows good care around others," Bailey said about Marsh, whose father Geoff and brother Shaun also represented Australia. "Performance is crucial from your captain. You want them to lead from the front. Mitch has done that particularly well in T20 cricket over time."

Marsh has intended to maintain a steady approach in the West Indies and United States, focusing on keeping the team relaxed off the field while remaining intense during matches. "One of the biggest things I've learned is to not change too much," he said. "A lot of preparation and planning goes into a World Cup, but once we're there, it's about keeping everything nice and relaxed, maintaining a good environment, and giving our all."

He added, "We have a great squad with versatility and experience, which brings a lot of excitement." Marsh, 32, can rely on advice from experienced teammates like his "great mate" Cummins, wicketkeeper Matthew Wade, and veteran opener David Warner, who is in his international swansong.

Despite former skipper Steve Smith not making the squad, Warner and Travis Head will open, with Marsh at first drop and Tim David and Glenn Maxwell as the big-hitting finishers. The bowling attack will be led by Cummins, Mitchell Starc, and Josh Hazlewood, with Adam Zampa as the wrist spinner and Nathan Ellis as an alternative medium-pace option.

Although England won the last World Cup and Australia were champions in 2021, Marsh insists there are no clear favorites. "If you look at this tournament now and the teams around the world, I don't think there can be a favourite," he said. "Five, six, or seven teams can win it. In tournament play, it's about getting things right at the right time and winning in big moments."

Marsh acknowledged the evolving nature of the game, particularly the trend towards aggressive power play. "The game's moving forward, teams are going harder in the power play. It's about assessing conditions and playing accordingly."

No team has held the T20, ODI, and Test world champion titles simultaneously, but Marsh believes it's premature to focus on such an achievement. "There are many hurdles to overcome at a World Cup before even getting a shot at that. That's for the external noise outside our group," he said. "But the carrot is there."

Australia, in Group B with England, to begin their campaign against Oman in Barbados on June 6.