Four-day Test matches could become mandatory as part of the World Test Championship from 2023, with the ICC's cricket committee likely to formally consider the change in 2020 amid widespread discussions among member boards about how to reduce numerous pressure points in the global cricket calendar for the future.

However, the world's cricketers stand as the most likely source of opposition to the change, with many viewing the step up from four-day first-class games to five-day Tests as a critical point of difference at the top end of the long-form game.

The ICC's increasing demand for event windows, the proliferation of domestic T20 leagues, the BCCI's demands for its own sizeable share of bilateral calendar space, and the costs of staging Test series are all factors contributing to the move, which would shave off a significant amount of time from the calendar for the 2023 to 2031 cycle.

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As an example, mandatory four-day Test matches rather than five-day matches during the current cycle from 2015 to 2023 would have freed up a total of 335 days of scheduled cricket over the period, a valuable amount of time that would also be enhanced by the ability to consistently schedule Test matches on a Thursday-to-Sunday basis, not dissimilar to the rhythm of golf tournaments on the world's major professional tours.

It would also allow for more Test series to played over three or five matches, affording host boards and broadcasters a greater share of the higher revenue-raising early days of a Test without having to budget for a fifth day. Australia's recent history against India has seen Test series played over four matches for a total of 20 scheduled days - the same number that would be scheduled for a five-match series of four-day Tests.

Matches played over four days would likely see the increase of the minimum overs in a day from 90 to 98, meaning that over four days only 58 scheduled overs would be lost. There has been an increasing proliferation in the number of Test matches finishing inside four days - more than 60% of matches played since the start of 2018 have ended in four days or fewer.

"If we have a clear picture of how it all works in an improved and well-structured schedule, then it would be something that could be taken to the players for their consideration" Tony Irish

"It is something that we have got to seriously consider," Cricket Australia chief executive Kevin Roberts told SEN Radio this week. "It is something that can't be driven by emotion, but it needs to be driven by fact. We need to look at what's the average length of Test matches over the past five-ten years in terms of time and overs.

"We need to look at it very carefully and perhaps it is more likely than not in the mid-term future. What we absolutely will do is that over the next 12 to 18 months, is make sure the cricket calendar is nailed down for the years 2023 to 2031. What we are committed to doing is working with all the ICC members - nobody is saying it is easy but what we are doing is looking at it holistically and we are committed to doing that."

The contrasting view, shared among many players, was provided by Australia captain Tim Paine at the conclusion of Australia's 247-run victory over New Zealand in Melbourne. "We might not have got a result if we'd done that in the Ashes, I think every game went to a fifth day," he said. "That's the point of difference with Test cricket, it is five days, it's harder mentally, it's harder physically, and it tests players more than the four-day first-class fixtures do. I think that's what it's designed to do, so I hope it stays that way."

Members of the ICC Cricket Committee at the two-day meeting in Mumbai International Cricket Council

A shift to four-day Tests would place an even greater premium on the quality of pitches around the world, with curators being required to provide a surface that aids pace bowlers, batsmen and spin bowlers over their course, without the chance of an extra day for the pitch to deteriorate over. It would likely also force captains to think more in terms of scoring rates and declarations to create enough time to bowl opposition teams put in the reduced time available.

Tony Irish, the head of the international players' body FICA, said that while four-day Tests would provide a solution to many of the game's growing problems around squeezing cricket's three formats into the global calendar, such a move could not be made without an integrated approach to scheduling and a far more "coherent" structure for the international game.

"There are two aspects to four-day Tests, the cricket aspect and the scheduling aspect," Irish told ESPNcricinfo. "It would take pressure off the schedule but our concern would be that the ad hoc way the schedule currently works they would simply plug in more cricket into the gaps. If introduced it therefore has to be part of a more coherent structure.

"We would need to understand exactly how the cricket aspects are intended to work and we would need to take that to the players. In the past, many players have been against a change to four days. However, if we have a clear picture of how it all works in an improved and well-structured schedule, then it would be something that could be taken to the players for their consideration.

"Unfortunately with the ICC there is a history of introducing these types of changes in an unstructured way and that would need to change. We reckon they need to do a lot of work on how the schedule will look and not just present it as a concept."

Four-day Tests have already been added to the calendar in a limited form, for matches such as a Test between South Africa and Zimbabwe, and then England hosting Ireland earlier this year. Australia will likely play its first four-day Test against Afghanistan at home next summer.