Ashton was initially omitted for Saturday’s showdown at Twickenham, but the wing could yet win his first cap for four years from the bench.
Centre Tuilagi will not feature against the Springboks due to a groin injury.
The Leicester Tigers powerhouse has been beset by injury problems and will have to wait for a first Test appearance in over two years.
Ashton scored a hat-trick on his Sale Sharks debut in a European Challenge Cup win over Connacht.
The flyer returned to his homeland to put himself back in contention for an international call-up after one outstanding season with Toulon.
England co-captain Owen Farrell said that centre “seemed in high enough spirits” despite the latest setback.
“I don’t think it is anything too serious, but obviously with his history, probably not one to risk.”
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