England will miss the services of Henry Slade, Sam Underhill and Ruaridh McConnochie for the upcoming World Cup warm-up game against Wales to be played at Twickenham Stadium on Sunday.
Flanker Underhill and centre Slade were also expected to start but have respective knee and toe problems.
Eddie Jones' team play Wales again in Cardiff on August 17 before two more warm-up matches against Ireland and Italy in London and Newcastle, respectively.
Meanwhile, Courtney Lawes and Manu Tuilagi have been added to the replacements bench.
Exeter Chiefs centre Henry Slade drops out with a knee injury and is replaced by Bath's Jonathan Joseph.
The New Zealand-born Heinz, 32, gets the nod at scrum-half while McConnochie is named on the right wing by Jones, who has selected George Ford as his fly-half and captain with Owen Farrell left out of the 23-man squad. Joe Launchbury, 5.Charlie Ewels, 6. Lewis Ludlam, Joe Marchant and Jack Singleton can also expect to win their first caps from the bench. Joe Marler, 18. Harry Williams, 19.
Both Heinz and McConnochie were surprise inclusions in the wider training squad, with Heinz now edging ahead of Ben Spencer in the battle to be Ben Youngs' back-up. George North, 13. Jonathan Davies, 12. Gareth Anscombe, 9. Gareth Davies, 1. Nicky Smith, 2. Ken Owens, 3. Aaron Wainwright, 7. Justin Tipuric, 8.
Replacements: 16. Elliot Dee, 17.