England have suffered a significant setback in their Guinness Six Nations title defence after Courtney Lawes was ruled out of the remainder of the tournament by a chest injury.
Lawes suffered damage to his pectoral muscle in training on Wednesday and misses Saturday's Cardiff showdown with Wales and the final two matches against France and Ireland.
"Unfortunately, Courtney picked up a knock and that means he won't be available for us for the rest of the Six Nations," attack coach Simon Amor said.
Lawes was due to continue at blindside flanker for the title clash at the Principality Stadium but his mishap on the training field means Mark Wilson starts in the six jersey.
It is a bitter blow to Lawes, who battled back from ankle surgery that forced him to miss the entire autumn campaign to regain his place in England's starting XV for the Six Nations.
Having been picked as a replacement for the opening-round defeat by Scotland, the 32-year-old veteran lock and flanker was then promoted to the back row where 87 caps of experience and defensive ferocity will be missed.
"We're waiting for more detail on the injury, but Courtney had a bit of a fall and he tweaked his pec," Amor said.
"It's very disappointing but these things happen. We'll look at a replacement after this Wales game.
"Courtney Lawes is an experienced player. He brings a line-out threat and a great defensive energy.
"But we've got some really fantastic players, particularly Mark Wilson who is one of our work-rate players.
"He can really get around the field and has that energy, particularly around the breakdown."
Lawes is England's third back row casualty of the Six Nations with Jack Willis missing the rest of the season because of a knee injury and Sam Underhill so far unable to take part due to a hip problem.
