Durban - England lock Joe Launchbury has been ruled out of the three-test tour of South Africa because of a knee injury, coach Stuart Lancaster said on Friday.
He will be replaced in the 42-man squad by uncapped London Irish flanker Jamie Gibson.
"Joe picked up a knock in training before we came out here and we had him assessed here and he is not going to be able to continue the tour," Lancaster told a news conference.
"We are delighted for Jamie coming in but it is hugely disappointing for Joe," he said of the London Wasps player.
Centre Manu Tuilagi also missed training with a foot injury but Lancaster was confident the New Zealand-born centre would recover.
England arrived on Thursday and Lancaster said he was pleased by the intensity shown by the players during their first training session ahead of the opening test in Durban on June 9.
"It was a great session and considering we stepped off a plane yesterday, you'd have thought there would be a bit of tiredness, but they didn't show it," said Lancaster.
"When you've got competition for places that is a critical thing. You know there's a real energy and buzz. We've got some difficult selections to make as we build into next week because we've got a lot of good players fit and in form."
The opening test will be the first in charge for home coach Heyneke Meyers.
"South Africa, with the new coaching team, will have new momentum and new impetus behind them. We expect a very physical and tough challenge," said Lancaster.