Despite being restricted to just one appearance in the top flight, Wilshere had been in contention for a place in the group to face Germany and Brazil due to his showings in the Europa League and EFL Cup.
However, Southgate has hinted that he had little option but to leave out the 25-year-old due to his lack of minutes at the Emirates Stadium.
The 47-year-old told reporters: "I don't know how you get in an England squad without getting in the Arsenal team.
"There is no question about his ability, his football brain or personality, we just need to see him playing before he comes back in because unfortunately there has been a history of injuries.
"I'll be having discussions with Arsene about him, we think he is a top player so for him it's about game time."
Wilshere won the last of his 32 caps at Euro 2016.