The 29-year-old is back in the squad after a year-long loan at Hertha Berlin.
Benitez said: "He did really well in Germany last season, scoring plenty of goals, and he has told me that he wants to stay at the club and fight for his position.
"But he also knows that this club always plays more than 60 games a season and that means there are opportunities. He will fight for his place."
Benitez added: "Voronin is doing well. Last pre-season he also did really well for us and then when he went on loan he had a very good season in Germany with Hertha Berlin.
"He has game intelligence, which is something we are always looking for.
"At this moment he is a Liverpool player. But it depends on him, he is continuing to work hard and is playing well so he will have a chance.
"It is good to have him back. When we signed him we were looking for a player who could play 'between the lines' as a second striker with quality."