McLaren has yet to name the teammate for Button next year.
Nov.12 (GMM) Martin Whitmarsh has not denied mounting speculation that Sergio Perez will be ousted by McLaren after Brazil's 2013 season finale.
Team sources are being cited by a growing number of authoritative publications as having revealed that Mexican Perez will be replaced by the McLaren-backed youngster and new Formula Renault 3.5 champion, Kevin Magnussen.
"Lots of people are being considered," team boss Whitmarsh, when asked about the rumours, said during the regular Vodafone teleconference on Monday.
23-year-old Perez's chances of keeping his seat appeared to have risen after a strong result in India, but he then struggled in Abu Dhabi.
"He's done a pretty good job throughout the whole year," said Whitmarsh. "Abu Dhabi was difficult. It was not quite the result that we wanted and he wanted but difficult weekends happen.
"I think overall he's done a good job and we're still talking to him."
He acknowledged the media speculation about Magnussen, the son of former F1 driver Jan, but insisted that McLaren's decision is not yet made.
"The fact is at the moment we haven't confirmed our driver lineup, we haven't signed contracts with drivers, and we're still talking about that," said Whitmarsh.
The mounting rumours about the identity of Jenson Button's 2014 teammate, and Whitmarsh's vague comments, coincided with Perez admitting in Mexico that 2013 has been "the most disappointing season in my career".
"It's my third year in Formula One and has been my most difficult year, the most disappointing season in my career," he is quoted by EFE news agency in Toluca, about 50 kilometres from Mexico City.
Perez added that the season was also "very frustrating" and "probably the worst season in history" for the successful McLaren team.
He said he has felt a "heavy responsibility" this year but argued that his contribution was limited "with a car that bad".