Jack Clifford has been called-up by England for their Oxford training camp after Billy Vunipola suffered a potentially-serious knee injury on Saracens duty.

Vunipola had to be helped from the pitch in the first half of yesterday's 41-13 victory over Sale and medics are awaiting the results of a scan that could see the number eight ruled out of the autumn series against Argentina, Australia and Samoa.

It was only the second match of his comeback from the shoulder surgery that forced him to miss the British and Irish Lions tour to New Zealand and he also damaged the same knee against Argentina last November, sidelining him for three months.

"Billy has had some cruel luck with injuries so we're all praying and hoping that this isn't too serious," Saracens director of rugby Mark McCall said.

Clifford had fallen out of favour with England having won all 10 of his caps under Eddie Jones, but his all-action display in Harlequins' 31-28 defeat by Leicester will have impressed the Australian, who was watching from the stands.

"This camp in Oxford is a really positive opportunity for the group to come back together and sharpen our focus and preparation ahead of our first match against Argentina," Jones said.