The Arsenal players were training on Christmas Day ahead of the Premier League clash against Southampton away from home on Boxing Day.
Arsenal defeated fellow title contenders Manchester City 2-1 at the Emirates Stadium in North London on Monday night.
Sheaf is a 17-year-old central midfielder who is technically very gifted and is very highly rated. The teenager is an England youth international who possesses the ability to shoot accurately from long range.
Hillock is also 17 years of age and plays as a winger. The England youth international is also very highly rated and is one for the future.
Kamara is 20 years old and plays as a defensive midfielder. The youngster features for Arsenal’s Under-21 side and is a Finland Under-21 international.