England are sweating over the fitness of Fin Smith as their first-choice fly-half battles a calf problem that places his involvement in the Nations Championship opener against Australia in doubt.

Smith is being assessed having entered England’s three-day training camp with the injury sustained in the second half of Northampton’s Gallagher Prem defeat at Leicester on Saturday.

Head coach Steve Borthwick is expecting an update on Tuesday and has called Charlie Atkinson into his 36-man squad as a replacement as preparations continue for the Wallabies’ visit to Allianz Stadium on Sunday week.

If Smith is ruled out, George Ford and Marcus Smith will compete for the number 10 jersey in the first of next month’s four Tests.

Ford started the first three matches of the Six Nations until Fin Smith took over as chief conductor and would provide an experienced alternative, while Marcus Smith is fresh from a virtuoso performance for Harlequins against Saracens on Sunday.

However, Smith is now primarily seen by…