Defenders Wesley Fofana and Benoit Badiashile are out of Chelsea's US tour squad.
Both players are recovering from injury and are joined in staying in London by Reece James and Armando Broja as they also do their rehab.
Meanwhile, Romelu Lukaku, Pierre-Emerick Aubameyang, Hakim Ziyech and Callum Hudson-Odoi have been left at home as they seek moves away.
Chelsea meet Wrexham on Wednesday, before also playing against Brighton (July 22), Newcastle (July 26) and Fulham (July 30). The tour ends on August 2 against Borussia Dortmund.
Chelsea's 29-man squad for USA pre-season tour:
Goalkeepers
Kepa Arrizabalaga
Gabriel Slonina
Lucas Bergstrom
Eddie Beach
Jamie Cumming
Defenders
Thiago Silva
Trevoh Chalobah
Ben Chilwell
Marc Cucurella
Malo Gusto
Bashir Humphreys
Levi Colwill
Ian Maatsen
Alfie Gilchrist
Midfielders
Enzo Fernandez
Conor Gallagher
Carney Chukwuemeka
Andrey Santos
Cesare Casadei
Lewis Hall
Forwards
Mykhailo Mudryk
Raheem Sterling
Noni Madueke
Angelo Gabriel
Diego Moreira
Nicolas Jackson
Christopher Nkunku
Mason Burstow
Dujuan Richards (training only)