Head coach Steve Borthwick has named a 36-player squad for the tournament, assembling at Pennyhill Park on Monday. In the absence of Mitchell, Bath scrum-half Ben Spencer and Bristol Bears' Harry Randall have been called into the setup as scrum-half options alongside Leicester Tigers player Jack van Poortvliet.

Mitchell sustained the injury during Northampton's 28-14 win at Franklin's Gardens, leaving the pitch after just 21 minutes. The 29-year-old has established himself as the first-choice number nine under Borthwick, making his prolonged absence a significant blow to England's preparations.

Compounding the scrum-half shortage, uncapped Northampton player Archie McParland is also sidelined after sustaining a calf injury during training with the national squad last week. Consequently, Borthwick faces a major reshuffle in the half-back department ahead of Sunday's opening fixture against the Wallabies.

Van Poortvliet, who started all three of England's summer Tests, is widely expected to wear the starting shirt at Allianz Stadium. Both Randall and Spencer offer contrasting strengths from the bench, with Randall renowned for his sniping running game and Spencer valued for his tactical kicking.

In other squad news, fly-half Fin Smith took a limited part in training upon arrival as he continues his recovery from a calf problem. England coaching staff remain optimistic about his availability for Sunday's encounter, though Harlequins playmaker Marcus Smith is also pushing for the starting fly-half berth.

Several other players are managing injuries within the 36-man group, including hooker Luke Cowan-Dickie and flanker Tom Curry. Both participated in modified training sessions at the Bagshot base but are expected to be fit for selection by the end of the week.

Borthwick's squad features 20 forwards and 16 backs as England return to Allianz Stadium for four consecutive Test matches. Following Sunday's clash with Australia in round four of the competition, England will host Japan in round five and New Zealand in round six.

The autumn series concludes with the finals weekend scheduled from November 27 to 29. Borthwick highlighted the importance of the upcoming matches, noting they provide a final opportunity to face southern hemisphere opposition before next year's Rugby World Cup.

"We're looking forward to getting back to Allianz Stadium for four important Test matches against top-level opposition," Borthwick said. "These fixtures take on added significance this autumn as they represent our final opportunity to face southern hemisphere opposition before next year's World Cup."

England squad: Forwards: Fin Baxter, Ollie Chessum, Arthur Clark, Alex Coles, Luke Cowan-Dickie, Ben Curry, Tom Curry, Theo Dan, Ben Earl, Greg Fisilau, Jamie George, Ellis Genge, Joe Heyes, Maro Itoje, Emmanuel Iyogun, George Martin, Asher Opoku-Fordjour, Tom Pearson, Henry Pollock, Will Stuart. Backs: Seb Atkinson, Fraser Dingwall, Immanuel Feyi-Waboso, George Ford, Tommy Freeman, George Furbank, Will Joseph, Joe Marchant, Cadan Murley, Harry Randall, Henry Slade, Fin Smith, Marcus Smith, Ben Spencer, Freddie Steward, Jack van Poortvliet.

The absence of their regular skipper forced a late leadership change for the side as they prepared to take to the field. In the absence of Das, middle-order batsman Tawhid Hridoy was handed the responsibility of leading the national team for the opening fixture against Zimbabwe.

Compounding their selection difficulties further, the Tigers were also forced to cope without the services of senior all-rounder Mehidy Hasan Miraz. The influential player was sidelined for the fixture due to a sudden bout of fever, leaving the playing combination severely depleted.

The timing of these absences represents a challenging moment for the team management as they attempt to build cohesion and momentum. Litton Das had only recently been appointed as the full-time ODI captain earlier in the year, taking over leadership duties from Mehidy Hasan Miraz.

The leadership transition was designed by selectors to establish long-term stability and strategic direction as the squad seeks to build up competitive readiness. Their ultimate objective remains preparations heading towards the upcoming ICC Men's Cricket World Cup scheduled for next year.

At the toss ahead of the opening fixture at the neutral venue in Abu Dhabi, fortunes favored the opposition camp. Zimbabwe won the coin toss and elected to bat first, putting immediate pressure on the makeshift Bangladesh bowling attack under the floodlights.

Despite the difficult circumstances surrounding the squad's preparation and fitness concerns, stand-in captain Tawhid Hridoy sought to lead by example on the pitch. During the innings, Hridoy demonstrated aggressive intent by going big and launching a delivery into the stands for a massive six.

The tri-series format sees all three participating nations facing each other in a round-robin schedule before the ultimate climax. Following the opening clash between Bangladesh and Zimbabwe, the fixture list continues with Afghanistan facing Zimbabwe on 19 October at the same venue.

The round-robin phase concludes when Afghanistan take on Bangladesh on 21 October in the United Arab Emirates. The top-performing teams from these preliminary matches will then contest the tournament final scheduled to take place on 23 October in Abu Dhabi.

Abu Dhabi has increasingly become a favored neutral venue for international fixtures involving various Associate and Full Member cricket boards. The neutral conditions offer all competing teams an even playing field ahead of more demanding global tournaments in the international calendar.

The reliance on younger leadership figures such as Tawhid Hridoy highlights a broader transition phase currently underway within the squad. Selectors are clearly prioritizing depth and blooding fresh talent to ensure the team can withstand injuries to senior players during crucial series.

Fitness concerns have frequently disrupted team selections for international touring parties operating in demanding overseas environments. Medical staff will continue to monitor Litton Das and Mehidy Hasan Miraz closely to determine their availability for subsequent matches in the series.

The absence of both the captain and a frontline all-rounder places immense pressure on the remaining members of the playing XI. Coaches will demand disciplined performances across all departments of the game to compensate for the missing experience against determined opponents.

Bangladesh cricket has experienced a turbulent period of transition following mixed results across various bilateral series and global competitions. Establishing a settled leadership group remains a primary target for the board administration and coaching staff alike.

Zimbabwe enter this tri-series looking to secure valuable competitive exposure and test their capabilities against higher-ranked opponents. Every match in the UAE provides crucial ranking points and tactical insights for their ongoing development program in limited-overs formats.

Afghanistan complete the three-team lineup, bringing a formidable spin attack and dangerous batting unit to the desert conditions. Their recent progress in limited-overs cricket makes them a challenging opponent for both Bangladesh and Zimbabwe in the coming days.

As the tri-series progresses towards its conclusion on 23 October, all participating boards will evaluate their squad depth. The performances of replacement players like Tawhid Hridoy will provide selectors with vital data ahead of major global assignments next year.

The tactical decisions made during this opening encounter will likely influence team strategies for the remainder of the tournament. Coaches must adapt quickly to the physical demands of playing international cricket in neutral territory without key personnel.

Supporters following the action from home will be eager to see how the younger players respond to the added responsibility. The management remains hopeful of a swift recovery for both Litton Das and Mehidy Hasan Miraz as the tournament schedule intensifies.

With the opening match underway and Zimbabwe setting an early target after winning the toss, Bangladesh face a stern test of character. How the team navigates these early setbacks will set the tone for their campaign in the United Arab Emirates.