The pair forged a great alliance at the back-end of last season but Chicharito has been short of full fitness after picking up concussion on the US tour.
Although Danny Welbeck is sidelined due to a hamstring strain, Dimitar Berbatov, Michael Owen, Federico Macheda and Mame Biram Diouf are also competing for places, but Hernandez will be hoping for his first start of the campaign at Bolton after scoring for Mexico against Poland.
"He was a young lad in his first season and I probably didn't think he was going to play as many games as he did," Rooney revealed in an exclusive in-depth interview with MUTV.
"Once he got into the team, he took his chance and the manager kept him in. He repaid the manager with goals and was brilliant for us last season - a big reason why we won the league.
"I'm looking forward to him doing the same, if not scoring more goals for us, this season."
The Reds' number 10 has no worries about those fretting that Hernandez will find it more difficult to find the net in his second season in the Barclays Premier League.
"Of course people know about him now but, if you look at all the top players around the world, people know how they play and it's still difficult to stop them," reasoned Rooney.
"I'm sure people will know a bit more about him this year but his movement is so good it's difficult to defend against. It won't be easy for players to defend against him whether they know about him or not.