England suffer front row blow
South African-born England prop Matt Stevens has been ruled out of the tour of South Africa after suffering a shoulder injury.
The versatile front row forward who can play on both sides of the scrum suffered a shoulder rotator cuff injury during England's victory over the Barbarians on Sunday.
With Elite Player Squad members Henry Thomas and David Wilson injured, 26-year-old Harden will join England training on Tuesday.
England coach Stuart Lancaster commented: "Firstly, it's really tough on Matt but he has been assessed by the medics and he wouldn't be able to train or play for some time. We wish him all the best but it's a great opportunity for Rupert, who has been the first choice tighthead for Gloucester this season and also involved in the Saxons during the Six Nations."
The 29-year-old Stevens, who only returned to rugby last year after serving a two-year suspension for testing positive for cocaine, is to be replaced by Gloucester's Rupert Harden.
It is a cruel twist for the Saracens prop, who had battled his way back into the England squad despite his lengthy enforced lay-off from rugby.
England, who depart for South Africa on Wednesday, are already facing concerns over the fitness of flyhalf Toby Flood and the availability of Leicester Tigers centre Manu Tuilagi.
Tuilagi could miss the entire tour to South Africa after being cited for a "tip" tackle on Danny Care during last weekend's Premiership Final against Harlequins at Twickenham.