Vickery will still travel to Rome with the rest of the squad
Date: Sunday, 10 February
Kick-off: 1430 GMT
Venue: Stadio Flaminio, Rome
BBC Coverage: Live on BBC ONE, BBCi, Radio 5 Live Sports Extra and BBC Sport website (UK users only).
Highlights on BBC Sport website (UK users only). Watch in full on BBC iPlayer for seven days from Monday (UK users only)
England captain Phil Vickery is a doubt for his side's RBS Six Nations clash with Italy on Sunday after suffering a calf injury in training.
Uncapped Bristol prop Jason Hobson has been called up as cover for the bench and will travel to Rome on Friday.
Vickery, who will also travel to Italy, would be replaced by Matt Stevens if he fails to shake off the injury.
Centre Toby Flood has also picked up a thigh strain, but is expected to shake off the injury in time to play.
Flood trained with the team for the first time this week on Thursday, but has not been kicking in order to protect his quadriceps muscles.
England have already lost five players to injury ahead of the match in Rome, with Vickery's fellow prop Andrew Sheridan ruled out earlier this week with an abscess and replaced by Wasps loose-head Tim Payne.
I didn't feel a pull, a tear or anything like that, it is just very sore
England captain Phil Vickery
Head coach Brian Ashton has also seen Mike Tindall (bruised liver), David Strettle (foot), Lewis Moody (Achilles) and Tom Rees (knee ligament) taken out of the equation by injury.
Ironically, Hobson was banned last season for punching Vickery in a Guinness Premiership match, forcing the England skipper to miss two Six Nations matches.
Vickery's potential absence will be a real worry for Ashton, with Italy's front row - which includes Leicester prop Martin Castrogiovanni - rated as one of the best in the tournament.
"I was doing some contact drills, I took the ball in and when I put the ball back I either caught a knee or a boot on my calf," said Vickery.
"I didn't feel a pull, a tear or anything like that, it is just very sore. I will probably know a bit more after it has been iced a few more times and the physios have looked at it.
"I don't want to sit here and say it's a 50-50 chance, because with all the goodwill in the world, I haven't got a clue.
"We have got a travelling day tomorrow (Friday), and we will see how it goes then."
Fly-half Jonny Wilkinson, who retained his place despite an out-of-sorts display against Wales last week, would be the favourite to take over the captaincy should Vickery fail to recover.
Many pundits called for Wilkinson to be dropped for the first time in an illustrious 10-year Test career, but Ashton resisted that option and kept the precocious Danny Cipriani on the bench.
"We talked it through, as we did every position," Ashton said. "But knee-jerk reactions are not part of my make-up. I am accountable for what we do."
Michael Lipman has been picked at open-side flanker while Nick Easter returns at number eight in place of Luke Narraway, who drops to the bench after his debut.
Jamie Noon comes in for Tindall at outside centre, and former rugby league star Lesley Vainikolo starts his first Test after making his England debut off the bench last week.
Lipman, born in London but raised in Australia, wins a fourth cap, which will be his first experience of the Six Nations.
The 28-year-old has been in impressive form in the Guinness Premiership this season, and Ashton said he was unlucky to miss out on the original 32-man training squad.
Easter has missed Harlequins' last four matches following a knee injury sustained on 29 December.
"We are looking forward to it," Ashton added. "There are one or two angry men - quite rightly so, they ought to be angry with themselves - in our squad.
"There was massive disappointment and incredible anger at what happened last Saturday, and hopefully we can turn that into a positive this weekend."
England: Iain Balshaw (Gloucester), Paul Sackey (Wasps), Jamie Noon (Newcastle), Toby Flood (Newcastle), Lesley Vainikolo (Gloucester), Jonny Wilkinson (Newcastle), Andy Gomarsall (Harlequins); Tim Payne (Wasps), Mark Regan (Bristol), Phil Vickery (Wasps - captain), Simon Shaw (Wasps), Steve Borthwick (Bath), James Haskell (Wasps), Michael Lipman (Bath), Nick Easter (Harlequins).
Replacements: Lee Mears (Bath), Matt Stevens (Bath), Ben Kay (Leicester), Luke Narraway (Gloucester), Richard Wigglesworth (Sale), Danny Cipriani (Wasps), Mathew Tait (Newcastle).