A number of overseas players are expected to withdraw from the inaugural season of the Hundred due to clashes in the international calendar and complications regarding international travel caused by Covid restrictions.

West Indies, Pakistan and Australia players with contracts to appear in the men's competition will have their availability limited if they are involved in the two T20I series due to take place in the Caribbean in July and August, while two Australia players - Rachael Haynes and Jess Jonassen - have already withdrawn from the women's tournament due to quarantine requirements.

Cricket West Indies announced its men's fixtures for the 2021 home season last week, with the end of the T20I series against Australia overlapping with the start of the Hundred. Seven of the nine Australians contracted to play in the men's competition were named in an enlarged 23-man squad on Monday - Chris Lynn and Nathan Coulter-Nile were the exceptions.

Those seven include marquee names in Aaron Finch, Glenn Maxwell and David Warner, and while it is possible that they could still play the majority of the eight-game group stage subject to quarantine periods, Cricket Australia remain in talks with the Bangladesh Cricket Board regarding a possible tour which would present a further clash.

Four West Indians are also under contract: Nicholas Pooran and Kieron Pollard are both key parts of the T20I set-up, while Andre Russell and Sunil Narine are likely to come back into the picture ahead of this year's T20 World Cup. Their series against Pakistan starts on July 27, three days after the Australia T20Is finish, with the fifth and final match scheduled for August 3 in Guyana - which is on the UK's travel red list, adding to the complications - though it is understood they remain keen to be a part of the tournament if possible.

Pakistan stay in the Caribbean for two Tests on August 12 and August 20, which will effectively rule Shaheen Shah Afridi out of his deal with Birmingham Phoenix. Shadab Khan, the other Pakistan player involved, may be available for the second half of the tournament with Manchester Originals if he is overlooked for the Test squad again.

The ECB remain confident that the Hundred will feature some of the best overseas players in the world but are realistic about the fact that some players will withdraw in the coming weeks and months. The new 100-ball tournament's inaugural season was postponed last year due to operational challenges, and is now due to start on July 21. "The realities of Covid mean there remain practicalities that are difficult for some overseas players to overcome," a spokesperson said.

Jonassen was replaced by compatriot Georgia Wareham in the Welsh Fire squad last month, while Haynes' withdrawal from her Oval Invincibles contract was revealed by London's Evening Standard last week. They are the only two confirmed withdrawals as yet, but the fact that salaries are significantly lower in the women's competition (£3,600-£15,000) than in the men's (£24,000-£100,000) reduces the incentives for players to travel to the UK specifically for the tournament. As such, it is possible that further Indian players will sign deals and stay on following the conclusion of their tour to England on July 15 - six days before the start of the Hundred.

In the men's competition, there is a broad pool of nearly 250 overseas players registered as replacements. Several of them, including Dan Christian, Glenn Phillips, Lockie Ferguson and Carlos Brathwaite, will already be in the UK to play in the T20 Blast for their respective counties, and as such may be attractive options, either to fill in for a handful of games or to play the full season in the event of withdrawals.

Meanwhile, Manchester Originals can begin to negotiate with county cricketers who were not signed in February's re-draft following Harry Gurney's retirement. Gurney was an £80,000 signing in the draft and his withdrawal from the competition means that there is a free slot up for grabs at that price bracket for any domestic player without a contract.

The ECB are hopeful that England's centrally contracted red-ball players will be available for up to three group-stage games at the start of the tournament before the start of the men's Test series against India, and potentially the eliminator and the final. Ashley Giles, the managing director of England men's cricket, said last week: "We've got a lot of cricket coming up so it's a difficult juggling act but I know the players are also looking forward to that tournament and would love to be involved at some stage if they can."

England men's players on all-format central contracts will earn £40,000 for their involvement in up to three matches, and those on red-ball deals will earn £28,000. All centrally-contracted players will then earn £4,608 per match for any additional fixtures. Players with white-ball contracts are due to be available throughout the Hundred, and are paid directly through the draft mechanism.