The 22-year-old, who was acquired by Newcastle from Norwich City for a fee of £10 million in July, has played a handful of matches, lasting only 199 minutes in total.
Atsu has made his season-long loan from Chelsea permanent in a four-year deal and has been one of the Magpies' top performers this season.
“You can use the money [the club used to purchase him] as an excuse for anything but Matt Ritchie and Christian Atsu also cost us money," Benitez told the Chronicle.
“The main thing is not the money. We signed a player for four or five years - who is a young player - who needed Premier League experience.
“He is getting better. In every training session, there is improvement from him and he is working hard trying to get better.
“I am really pleased with everything. I think he will be a good player for us during the season and also in the future. He is still a young player,” he added.
Atsu has played every single game in the Premier League this season, scoring one goal and providing two assists.
Newcastle sit seventh on the log with 14 points, one place above Burnley, who they will face at Turf Moor on Monday, with the Ghanaian likely to maintain his starting place.