There was a favourable result of an x-ray on Trott's injured right hand on Monday, but the England and Wales Cricket Board have taken the precaution of adding Somerset batsman Buttler to their squad. Number three Trott was struck a painful blow by a short ball from Dale Steyn during England's six-wicket win at Lord's yesterday.
After he had shown obvious signs of discomfort during a century stand with Ian Bell, there were fears he might have broken bones. Monday's ECB report on his condition was encouraging, but it was decided nonetheless that 21-year-old Buttler should provide extra cover.
Buttler has played just one previous one-day international, against Pakistan in Dubai earlier this year, but has featured in eight Twenty20s for his country and is in England's 15-man squad for the defence of their ICC world crown in the shortest format in Sri Lanka this month.
He comes into a NatWest Series squad in which Jonny Bairstow is already an obvious possible replacement should Trott's injury prevent him playing at Trent Bridge on Wednesday when England are hoping to close out series victory after taking a 2-1 lead at Lord's.
The ECB update on Trott's injury read: "X-ray of hand rules out any major fracture.
"Further medical assessment required tomorrow."