The England global then became involved in a shoving match with Tyreke Wilson after the City defender ran up to confront him, and the incident sparked further unrest between the players.
The midfielder spent last season on loan at Bournemouth after having the previous campaign ruined by injury and has made just five league appearances for the Gunners in the last two years.
The 25-year-old - now fit again following his recovery from the fracture to his lower left leg suffered during Bournemouth's 4-0 defeat at Tottenham in April - was drafted into Steve Gatting's side on Tuesday night, along with fellow first-team squad players R ob Holding and Ainsley Maitland-Niles.
Despite SIDS risk, 56% of parents inconsistently use safe infant sleep positions
Since 2005, the AAP recommended infants be placed exclusively on their backs to sleep - the "gold standard" of sleep positioning. For the new study, researchers examined survey data collected from 3,297 mothers of infants from 2 to 6 months old.
After getting to his feet, Wilshere squared up to Smith before pushing him in the chest.
Once calm was restored, the referee showed the red card to both Wilson and Wilshere.
Wilshere had produced an encouraging performance until that point, including a excellent assist for Arsenal's third goal, scored by Eddie Nketiah.
Arsenal Under-23s ran out 4-3 winners at the Emirates.