Northampton Saints scrum half Lee Dickson was last night ruled out of Sunday's game and next month's Churchill Cup to have surgery on shoulder injury.
Head Coach Lancaster said: "We've also got a couple of other injuries to assess and we'll have a look at some potential replacements in training today against the England Under 20 side. Another 24 hours will give us time to finalise the squad before we move to Pennyhill Park and train at Twickenham on Friday.
"Our preparations have gone well overall and we're pleased to announce that Luke Narraway will captain the side which is a great reflection of the form and leadership qualities he's demonstrated at Gloucester this season."
England have a number of experienced backs at their disposal for the non-cap game - including Charlie Hodgson (Sale Sharks), Matt Banahan (Bath Rugby), Ugo Monye (Harlequins) and James Simpson-Daniel (Gloucester Rugby).
In a group of young forwards the likes of prop Joe Marler (Harlequins), lock Graham Kitchener (Worcester Warriors) and flanker Carl Fearns (Sale Sharks) are set to make their first senior appearances at Twickenham.
Exeter Chiefs flanker Tom Johnson, one of the discoveries of the season in the Aviva Premiership, will get to pull on an England shirt at 15-a-side level for the first time this weekend.
Tickets are available for England against the Barbarians via RFU.com, with adult £25 tickets currently 2-4-1.
