Red Bull Racing team principal Christian Horner has said he wouldn't have retained Felipe Massa for F1 2013.

Massa's form early on this season was abysmal and while he did turn things around and now reckons he is 'more motivated than ever', Horner isn't convinced he would have made the same call as the Scuderia.

"No, I don't think I would have [re-signed him]," Horner told The Official Formula 1 Season Review 2012 book. "Unfortunately, it's a tough business, and results-based.

"You've got to look at what the guy in the other car, which we must assume is equal equipment, is achieving.

"They obviously had a look at other drivers - at least one of ours! - so they were obviously concerned about his form, but their options seemed to become limited.

"They took their time over [Sergio] Perez who, at the early point of the year, seemed to be a shoe-in for that drive. He'd shown real progress, he was a member of their junior academy, and then McLaren announced him.

"Then Felipe obviously picked his form up in the last third of the year. They were obviously deliberating - the messages coming out of Maranello confirmed that - and probably when the music stopped they realised that the option they had was best for them."