The Leicester flanker, substituted after straining his right calf against Wales, said: "There's a slight tear but we will know how bad over the next 48 hours.
"I've never had a calf strain before and I've had only three injuries that have kept me out for more than a week since I started my senior career.
"I've been very lucky, but I'm a quick healer and I'll be doing everything I can between now and whenever to get it right."
While England coach Clive Woodward, already almost certainly without injured props Phil Vickery, Julian White and Jason Leonard - along with back-row Lewis Moody - for the rest of the Six Nations campaign, is left to sweat over the fitness of Back, he had better news over Jonny Wilkinson.
The fly-half, who limped out with a knee injury in the second half in Cardiff, hopes to be fit to play for Newcastle at Wasps on Saturday.
Full-back Jason Robinson, who was also forced off against Wales with a knee injury, will undergo a precautionary scan this week and with his club Sale having no match scheduled this weekend, is hoping to be fit to face Italy.