Barrett missed last weekend's win over Coventry after suffering concussion against Watford the previous Tuesday.
Davis replaced Barrett on Saturday but was forced off during the first half with flu.
Hull loanee Anthony Gardner came on for Davis having recovered from a groin injury and could start alongside skipper Paddy McCarthy at the back.
Boss George Burley could otherwise stick with the side which secured a second straight win at the weekend to move Palace off the foot of the table.
Lee Hills and Sean Scannell are still out with knee injuries although the latter has returned to training.
Source: PA
Source: PA