Wicketkeeper-batsman Sam Billings has been added to the England squad for the final Ashes Test against Australia in Hobart as cover for the injured Jos Buttler and Jonny Bairstow, the country's cricket board (ECB) said on Friday.

Buttler suffered a blow on his left index finger during the second day's play in Sydney on Thursday, while Bairstow batted through pain en route to a gritty hundred earlier on Friday after being struck on the thumb by Pat Cummins.

Asked about the extent of his injury, Bairstow said: "I don't know as yet... I'll know some more information tomorrow. I'm not sure about the keeping side of things. But from a batting point of view, I'll be out there in the morning."

READ: Bairstow's century drives England fightback in Sydney

Billings, who has yet to make his debut in the longest format, was recently in action for the Sydney Thunder in the Big Bash League Twenty20 competition.

"(Billings) was due to fly to the UK this evening ahead of England's T20I tour of the Caribbean. He will now join the Test party in Sydney after a period of isolation in the team hotel subject to receiving a negative PCR test result," the ECB said in a statement.

England, which is already 3-0 down in the five-match series, finished day three of the Sydney test on 258-7, 158 runs behind Australia's first-innings total. The final test starts on January 14.