Marcus Smith has been ruled out of England’s Six Nations opener against Italy on Saturday because of a calf injury with Steve Borthwick in the dark over whether the Harlequins fly‑half will miss the entire championship. Fin Smith is in line for a Test debut as a result and has been declared “ready to start” if Borthwick opts to hand the 21‑year‑old the No 10 jersey in Rome.

England’s problems are ­mounting before the start of their campaign with Alex Mitchell also handing the head coach a sizeable scare. The Northampton scrum-half has been unable to train all week because of an infected wound in his leg, further disrupting Borthwick’s preparations.

Marcus Smith sustained his calf injury at England’s training camp in Girona on Monday and was later seen on crutches at the team’s base. An initial scan has ruled him out of contention for the opening round of the Six Nations with Borthwick ­waiting on a second opinion to determine the length of his absence.

It is a bitter blow for the Harlequins fly‑half and for Borthwick who, after Owen Farrell’s decision to make himself unavailable, is believed to have been strongly considering starting Marcus Smith in Rome. Without him, it is a shootout between George Ford and Fin Smith to start on Saturday.

“[Marcus] won’t make this ­weekend sadly,” the assistant coach Kevin Sinfield said. “We got the scan report through but we are waiting to understand exactly what that means for us moving forward. He’s not fit for this weekend. We’re waiting for a second opinion on the scan. We will know more then.

“[Marcus is] a big loss but what that does is provide ­opportunities for ­others. Fin Smith’s been in camp before – his form has been out­standing for ­Northampton and he has trained great, too. You don’t have to be a rocket scientist to figure out where that might leave us. We have got Fin and George, who has got 91 caps I think, so he has got that experience and a young gun who has been in top, top form. We’re still in a very, very good position.”

Mitchell, meanwhile, is understood to have sustained his leg wound before joining the squad in Girona. England are hopeful the Northampton player will still be declared fit for the match against Italy but question marks linger after he was forced to sit out training ­sessions on Monday and Tuesday. Danny Care and Ben Spencer are the other scrum-halves at Borthwick’s disposal. The head coach has already lost Ollie Lawrence and Luke Cowan‑Dickie since ­naming his squad while George Martin, Manu Tuilagi, Anthony Watson, Jack van Poortvliet and Tom Curry are also out with injury.