Launchbury only linked up with England yesterday after being called in as injury cover for Tom Palmer but he has been preferred to both Mouritz Botha and George Robson.
England head coach Stuart Lancaster will finalise his starting XV on Thursday, with Launchbury likely to be on the bench as back-up to Palmer and lineout general Geoff Parling.
Launchbury is one of three uncapped players in the 23-man squad, although the inclusion of Saracens loosehead prop Mako Vunipola and Leicester hooker Tom Youngs had been well signposted.
Vunipola is expected to join Launchbury on the bench while Youngs is due to start in place of the injured Dylan Hartley, just three years after he switched from being a hard-running centre.
Botha and Robson were among 10 players released back to their clubs tonight, a list that included loose-forwards James Haskell and Ben Morgan.
As a result, Thomas Waldrom appears to have retained the England number eight jersey while Tom Wood and Tom Johnson have both been preferred to Haskell and are vying to start at blindside flanker.
Wood has been included in an England matchday squad for the first time in nearly 14 injury-plagued months. The Northampton flanker's last appearance was against Romania at the World Cup.
"We have had a good two days back at Pennyhill Park and the players have been very focused on delivering against Fiji," Lancaster said.
"Saturday is a great opportunity for us to put a marker down and deliver a quality performance.
"It's great to have young players such as Mako Vunipola and Joe Launchbury get their opportunities in the matchday 23 and we are excited about the potential of the squad.
"We were keen to get Joe in, particularly in light of his recent form."
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