England prop Andrew Sheridan ruled out of Six Nations
Sheridan out of Six Nations - Johnson
Prop Andrew Sheridan will miss England's two remaining Six Nations matches after suffering a torn calf in Saturday's 17-9 win over France.
The 31-year-old, who missed the win over Italy a fortnight earlier with a back injury, was replaced by Alex Corbisiero before half-time.
Manager Martin Johnson said Sheridan could be out for up to four weeks.
Fly-half Toby Flood is likely to be fit to face Scotland on 13 March after having a scan on his Achilles.
"Flood is okay. He has a bit of Achilles tendon soreness. We think he will be fine, but we will be very cautious with him this week," said Johnson.
The lingering doubt over Flood's fitness means England have kept fellow stand-off Jonny Wilkinson with the squad and he will not be released to play for club side Toulon against Clermont this weekend.
Bath wing Matt Banahan, who was not in the original group of 20 players who convened in Oxford this week, has also been called into the squad for training.
With Bath prop David Wilson also injured, Gloucester's versatile Paul Doran-Jones - the only member of the group not on duty against France - was also retained, while Leeds duo Hendre Fourie and Steve Thompson were released to play in their side's vital Premiership match against London Irish on Sunday.
Scotland will be desperate, and desperate is not a bad way to play rugby sometimes
Johnson revealed that Sheridan's injury was a "grade-two tear" - the second of three degrees of severity.
Corbisiero is likely to deputise for Sheridan at loose-head after impressing against strong Italy and France front rows in England's last two matches.
Should he win selection, the 22-year-old London Irish man will complete a youthful England front row alongside hooker Dylan Hartley, 24, and tight-head Dan Cole, 23.
"When 'Sheri' ricked his back before the Italy game, it was almost good fortune that 'Corbs' got a start there, so he wasn't brand new to Test rugby when he came on for what was a big test against France," said Johnson.
"The good thing is when these guys come in, it has been pretty seamless. That is the benefit of the squad system, having these guys in training behind the scenes."
Sheridan's latest injury will also come as a concern to club side Sale, where he recently signed a contract extension to remain at Edgeley Park until the end of next season.
Capped 38 times by his country, Sheridan missed the entire 2010 Six Nations campaign after dislocating his shoulder in Heineken Cup action against Cardiff Blues in October 2009.
The injury required a reconstruction of the joint and, after almost a year out, Sheridan returned to action against Newcastle in September 2010.
England are hunting a first Six Nations title since 2003 and could claim the trophy and a Grand Slam with victories at home to Scotland and against Ireland in Dublin on 19 March.
But Johnson has warned his side against complacency against the Scots, who have lost their opening three Six Nations matches.
"We need to have the same mentality we had when playing the French," he added. "We knew they could hurt us if we didn't go out and play, and I thought our defence went up a notch.
"We need it to go up again because Scotland will be desperate, and desperate is not a bad way to play rugby sometimes...a chip on your shoulder, desperately trying to win. That is a good place to be.
"We need to be equally desperate in the right way, and be patient with what we are doing. It is going to be another battle."
England have not lost to Scotland at Twickenham since 1983, but have suffered memorable upsets against the Scots in the past, notably in 1990 and 2000, both at Murrayfield. Scotland have won two and drawn one of the countries' past five meetings.
"You really worry about games like Scotland," Johnson added. "They have shown some really good touches and beaten South Africa recently.
"Just because they have had a couple of defeats, it doesn't make them any less dangerous."
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