Scrum-half Willi Heinz has been ruled out of England's Six Nations finale against Italy with a leg injury.
Northampton's Alex Mitchell, 23, has been called up, with Wasps' Dan Robson and Leicester's Ben Youngs already in the 36-man group.
Uncapped Mitchell had been named in an earlier England training squad.
England could seal the Six Nations title with a win against Italy on Saturday if the result of France v Ireland goes their way.
"We'll see how he recovers this week," England defence coach said of Heinz's "soft-tissue injury".
"It's important that we get on top of it. Soft-tissue injuries can be very tricky so you can't afford to be too hasty."
Youngs, 31, is set to earn his 100th England cap on Saturday, while Robson will be hoping to win his third.
Gloucester's Heinz was a surprise inclusion in head coach Eddie Jones' 2019 World Cup squad but has since become an England regular.
The 33-year-old joins a growing list of unavailable players, with Exeter hooker Luke Cowan-Dickie, club-mate Jack Nowell, Saracens' Elliot Daly, Leicester fly-half George Ford and Harlequins prop Joe Marler also out of the game in Rome.
Northampton lock Courtney Lawes and Sale centre Manu Tuilagi are long-term absentees.
Bath scrum-half Ben Spencer - who flew to Japan as injury cover for Heinz ahead of the World Cup final - continues to be overlooked by Jones despite his impressive recent Premiership performances.
Jones will name his team to face Italy on Thursday.
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