"Calum has decided to shorten his holiday and come back on Friday," Wenger told Arsenal.com.
"He didn’t play in the under-21s and needs preparations.
"Welbeck isn’t completely recovered from the problem he had [at the end of last season]. He’s not back in full training so he will stay behind.
"Rosicky will stay back because he got a small injury at his last game against Iceland with Czech Republic.
"Ospina is on holiday until July 27 and Alexis is on holiday until August 3. Serge Gnabry is on holiday after playing with the under-21s. He’s back on July 20."
Arsenal squad (subject to change): Chuba Akpom, Mikel Arteta, Hector Bellerin, Santi Cazorla, Petr Cech, Calum Chambers, Francis Coquelin, Dan Crowley, Mathieu Debuchy, Mathieu Flamini, Gabriel, Kieran Gibbs,
Olivier Giroud, Alex Iwobi, Laurent Koscielny, Emiliano Martinez, Per Mertesacker, Nacho Monreal, Alex Oxlade-Chamberlain, Mesut Ozil, Aaron Ramsey, Jeff Reine-Adelaide, Wojciech Szczesny, Theo Walcott, Chris Willock, Jack Wilshere, Gedion Zelalem