England scrum-half Ben Youngs has been ruled out of Saturday's Test with Argentina after failing a fitness test on his hip injury.
The Leicester and Lions half-back had been named among the replacements for the Twickenham clash but has failed to recover sufficiently from the niggling complaint.
Youngs' place on the bench will be taken by Danny Care, who impressed during Harlequins' win at Leicester last weekend.
England head coach Stuart Lancaster said: "Ben is still suffering some discomfort in his hip area and is unable to run at full pace.
"He is making good progress and should be fit for consideration next week. We are fortunate that we can call on Danny who has been playing well for Harlequins and training hard with us."
One of the primary aims for the game against Argentina will be for England to improve the effectiveness of their attacking play.
Billy Twelvetrees and Joel Tomkins made a joint total of 14 metres in the win over Australia last week and failed to fashion a single line-break - backs coach Mike Catt is aware that is a statistic that needs to be bettered against the Pumas.
"All of us were a little bit disappointed with the attacking performance against Australia," said Catt.
"But looking at the detail of the game, when you don't get the ability to gain momentum from your set piece it doesn't work for you.
"It's about having patience and when the one or two opportunities do come our way we need to make sure we take them.
"What happens is players get frustrated by that, so it's a learning curve for them to not allow that to happen.
"We want the set piece we need against Argentina so we can generate the type of ball guys like Billy and Joel thrive on and release the likes of Chris Ashton, Ben Foden and Mike Brown.
"We'd like it to be nice and dry so we can really move Argentina around."