Steve Harmison is doubtful for England's Stanford Super Series opener against Middlesex on Sunday.
The Durham paceman fractured his left wrist during Durham's County Championship-clinching win over Kent at the end of September and has not yet fully recovered.
He took part in the first training session of the Caribbean trip on Saturday with strapping around the problem area, but also reported feeling unwell after arriving in Antigua from a bowlers' training camp in Barbados.
"Steve still has a little niggle which we will take advice on," said England coach Peter Moores.
"It might be that it is a bit early, so he might miss out.
"He has also felt a little bit sick today, nothing major, just some tummy trouble, so that might stop him playing. We will speak to the doctor and see what he says."
England, therefore, will not necessarily begin their preparations for the $20 million winner-takes-all match against the Stanford Superstars on November 1 with the settled side which dismantled South Africa in the recent NatWest Series.
"It was a very settled side and it looked a good side," added Moores.
"They have all played very good cricket and put themselves in a strong position to play.
"Possession is always a good thing for a player and they have certainly done themselves no harm by playing very good cricket for four games and beating South Africa 4-0.
"That was 50-over cricket, this is Twenty20, so this is slightly different - but we have a settled formula over how we play one-day cricket and it looks strong."
Left-arm seamer Ryan Sidebottom, himself just returning from a series of injury niggles, appears the most natural replacement for Harmison.
Sidebottom came through Saturday's practice session - during which England used the signature Stanford black bats outdoors for the first time - unscathed.
"He hasn't had much match practice but he is now physically fit enough to bowl off his full run," said Moores.
"We have got a few things to have a look at to make sure we are settled.
"The shape of the side will be pretty similar but it is a chance for us to look at different things.
"You look at the ground, the balance of spin against pace, whether we need extra batting etc etc. Over the week we will get an idea of what suits the pitch and conditions best.
"We have got a pretty versatile squad. In the summer we played the four heavy seamers, we have also got someone like Graeme Swann, who is a very talented off-spinner and so we will see which way we go tomorrow after a chat with Kevin (Pietersen, captain)."
Despite the life-changing sums of money on offer, Moores insists there is a relaxed feel to the 15-man squad.
"At the moment it is like first day back at school, it's exciting, we have had a longer break than we normally have, so we are fresh and everybody is raring to go," he said.