Felipe Massa's inconsistent race finishes cost him his place in the Ferrari team, says the company's president Luca Di Montezemolo.
He said Massa was an "exceptional guy and a wonderful person", but added: "In 2012, we felt the lack of his points in the constructors' [championship]."
And Fernando Alonso was kept informed about the choice of new team-mate Kimi Raikkonen, according to the Italian.
"Alonso is the first to be happy that he is coming here," he said.
Last week, Ferrari confirmed Lotus driver Raikkonen had agreed a two-year contract, starting from next season.
Di Montezemolo, who took the decision to replace Brazilian Massa with Raikkonen following the Italian Grand Prix, said: "The relationship [with Felipe] was clear. He needed results and so did we.
"He did get some, but he was inconsistent, having some good races but not on a regular basis. It will be good for him to have a change of scenery."
It is not clear where 32-year-old Massa's future lies, but he is being linked with the 2014 Lotus seat vacated by Raikkonen.
Ferrari's decision to partner Alonso, 32, with the Finn signals a return to the policy last employed between 2007 and 2009, when Raikkonen and Massa competed on equal terms.
Either side of that period, with Michael Schumacher from 1996-2006 and then with Alonso for the past four years, there has been a clear number one driver.
Speaking about suggestions Alonso was not informed of Raikkonen's arrival, Di Montezemolo added in Gazzetta dello Sport: "We are not masochistic enough to take on a driver without informing Alonso.
"Fernando was always in the picture regarding the choice, taken partly because employing a youngster, in what will be a complex 2014 season, did not inspire confidence.
"In a nutshell, I wanted a driver who would not make me regret Massa [leaving]. What I ask of Raikkonen is wins, a consistent performance level and podiums and Alonso will be the first to benefit."