The 24-year-old Spaniard replaced debutant Kieran Tierney in the 77th minute and made an instant impact, teeing up Joe Willock for Arsenal's third goal.
Bellerin was a key figure in the starting XI for Arsenal prior to his injury, but Emery is not anticipating the full-back being fast-tracked into the team for Monday's trip to Old Trafford.
Asked about Bellerin at a media conference, Emery told reporters: "He wanted to play 90. He said I'm ready and wanted to play.
"I think no [he won't be ready to start against Manchester United]. Maybe in his mind yes. We need to listen to the doctor.
"The first minutes were amazing for him...The most important for him is his attitude. He wants to help us."
Rob Holding marked his comeback from a knee problem that kept him out for nearly 10 months with a thumping header to put Arsenal 2-0 up.
"It is perfect to have more options at centre back. His spirit, his positive minutes. Every day in training he helps us to have more performances like a team," Emery said of Holding.
"He needed to take minutes and confidence. It was a perfect match. He was a little tired at the end, he's happy."
Gabriel Martinelli opened the scoring on his first start for the club and the 18-year-old rounded off a rout with a deflected stoppage-time strike.
"We were waiting and watching him [Martinelli], how he could improve with us," Emery added. "He played very well in pre-season, he was working each training with a big spirit and performance.
"I spoke with him and told him to have some patience for his opportunity to do like he was doing. Tonight he did that. He deserved it.
"He is very humble, he fights, he's hungry to have that opportunity to help us."