Fin Smith faces a make-or-break training session on Wednesday to prove his fitness for the No 10 jersey in England’s autumn opener against Australia on Sunday amid cautious optimism the Northampton playmaker will come through unscathed.

Smith sustained a calf injury in Northampton’s derby defeat by Leicester last month and the England head coach, Steve Borthwick, has been sweating on his fitness ever since. Smith’s Northampton half-back partner, Alex Mitchell, meanwhile, has been ruled out of England’s entire autumn campaign owing to his latest hamstring injury

The 24-year-old Smith came through a running session at England’s training base on Monday before being put on a modified programme and sitting out most of Tuesday’s session. There is a degree of positivity within the camp he remains on track but he will be put to the test in Wednesday’s full bore session before Borthwick finalises his side.

“I think he’s tracking nicely,” said Smith’s Northampton teammate Tommy Freeman. “He’s doing the right stuff with the physios. It’s always good having him and the connection I have with him at the club will always be beneficial, for me anyway.”

Should Smith be available it would be a major boost for Borthwick given he has started the last five Tests at fly-half and cemented his status as England’s first-choice No 10. George Ford and Marcus Smith are alternative options should Fin Smith lose his fitness race.

Mitchell, meanwhile, will miss England’s Tests against Australia, Japan and New Zealand as well as their placings match on Nations Championship finals weekend. The Northampton scrum-half had already been deemed unavailable for this weekend’s clash against the Wallabies and a scan on Monday has determined that Mitchell will sit out all of England’s autumn campaign.

As a result, Jack van Poortvliet is expected to start at scrum-half against Australia with Ben Spencer and Harry Randall vying for a spot on the bench. For Mitchell, however, it is rotten luck given his premature withdrawal against Gloucester last Saturday marked the fourth time this year he has suffered a hamstring injury. “To see him go off like that is not nice, but these things happen,” added Freeman. “It’s sport. It comes with the game. But we’re gutted for Mitch and hopefully it’s a good recovery for him.”

Mitchell suffered similar injuries during the Six Nations, at an England camp in May – recovering to take his place in the Northampton squad for the Prem final win over Exeter – and during the summer Test against Fiji. Van Poortvliet was England’s starting scrum-half for the summer given Mitchell’s lack of game time but when fit and firing the Northampton player is England’s first-choice No 9.

Already, Borthwick is without the Bath back-rowers Guy Pepper and Sam Underhill while the club’s rookie hooker Kepu Tuipulotu is also missing with a knee problem. Bristol’s centre Benhard van Rensburg is also absent after sustaining a nasty concussion against Northampton earlier this season, having also done so in England’s final match of the summer against Argentina. Archie McParland, Mitchell’s fellow Northampton scrum-half, is also unavailable with a calf injury but England are hopeful he will feature later in the campaign.