American Horner, who will ride for Lampre-Merida in the Spanish grand tour, said the pair were the leading contenders for the red jersey in one of the strongest Vuelta fields in recent memory.
Froome is Team Sky's number one, while Quintana will be attempting to win for Movistar.
"Chris Froome, because of the way he climbs and the way he time trials and also Quintana," Horner told AS.
"Nairo surprised me in the Tour in 2013 and in the Giro in 2014. He's an amazing climber.
"The battle between these two riders and the rest of the field should be brilliant. The Vuelta's always a great race."
Horner is given an outside chance of repeating his 2013 heroics, although he would have to break his own record - his Vuelta triumph made him the oldest grand tour winner, aged 41.
"I'm in good form. I'm proud to be defending my Vuelta title, to battle for it as strongly as possible," Horner said.
"I love this race, it was the biggest win of my career. The key is to stay healthy for all three weeks."
Also set to contend will be Tinkoff-Saxo's Alberto Contador, a two-time winner, and Omega Pharma QuickStep's Rigoberto Uran.
The three-week race will feature 21 stages, including three time trials - two individual and one team.
The peloton will encounter eight-summit finishes in those stages, including stage 11 - which sees the riders travel 153.4 kilometres from Pamplona to San Miguel de Aralar.