Barkley's return coincides with Youri Tielemans' season being ruled over due to injury.
Barkley is back from a knee injury suffered in January and Emery said: “We signed him because he was performing fantastically last year at Luton, and because of his qualities, his skills - we liked and needed him.
“Of course, when he's been consistent and playing, being a substitute player but always making a good impact, it was fantastic. He scored goals as well, and we got some points and he helped us a lot.
“When he was injured in January, February, March - more or less three months - of course we were missing him.
“We were missing the minutes he was giving us, playing, performing, and his consistency. And now again, it is the moment for him. He played the last match he played.
“He's feeling good enough again to help us with his qualities. And tomorrow, the same - we will need him to be ready, in case he's playing in the starting XI or in case he's playing as a substitute.”
Barkley's chance
Ahead of today's clash with Bournemouth, Emery added: “It is the moment for Barkley.
“Barkley, he is here for it. When we have some injured players, or we have some players not getting fit like we need, or maybe getting tired, we need players."