He noted that the club had conditions going into the market and that had a big effect on the team's ability to secure more deals in this concluded window.
"I think he's more likely to have an impact as a technical, continuity player, than necessarily a player that raises the level of the entire team".
Emery, asked if Denis will start tomorrow, said he has not taken a decision yet.
His move to Arsenal brings a reunion with Emery, who coached him during a previous loan spell at Sevilla, where they won the Europa League together. "The possibility and capacity is all different".
"After, he played with Barcelona, not in the first XI a lot of times, but he helped them there and played in the Champions League, in an important team with important players".
"But obviously we need to learn and look forward, learn about our mistakes and think about the next games".
The Gunners head into their trip to The Etihad on the back of their victory over Cardiff City at The Emirates in midweek.
The 25-year-old, who made one senior appearance for City during an earlier spell at the club, was the only arrival for Arsenal - who were hamstrung by having no money to spend on permanent signings.