Valencia's fellow Ecuadorian collapsed and died of heart failure in July, aged just 27.
The news shook an entire nation, including Valencia, who has also had a tattoo on his arm in tribute to Benitez.
"It is terrible that he passed away," Valencia told MUTV.
"He wasn't just a friend but a brother to me.
"I dedicated the tattoo and the goal celebration, and hopefully every other goal celebration, to him.
"We all loved him and it had a huge effect on the whole country.
"He was a top guy. He was humble and worked very hard to provide for him family. He was good fun to be around.
"It was unbelievable news to hear that at 27, he is going about life normally, then the next thing you see is that he has passed away."
After scoring just once last season, Valencia has been challenged to get "seven or eight" by manager David Moyes, which would represented his highest total since joining United in 2009.