Red Bull's head of aerodynamics in Peter Prodromou is on the brink of returning to McLaren as they look to rebuild after a torrid year, with Whitmarsh confirming in Japan a contract has already been signed.
It is understood Prodromou was in line to succeed Adrian Newey at Red Bull come the day the team's chief technical officer decided to step down with the Milton Keynes-based marque.
Prodromou has been a key player in Red Bull's dominance over the past few years, with the team on the brink of winning a fourth consecutive drivers' crown with Sebastian Vettel in Japan this weekend.
A Red Bull spokesperson would only state: "Peter has worked with Red Bull Racing for a long time.
"He's a valuable member of the team, and there's some considerable time remaining on his current contract with us.
"We would be very happy to continue working with him in the future, He's part of a very strong technical team, led by Adrian Newey."
A week ago, however, Whitmarsh announced his marque was in the throes of being considerably strengthened as they work towards 2014, and in particular 2015 with the arrival of Honda engines.
At the time, Whitmarsh said: "We can never - and certainly this year - be satisfied with where we are.
"So we've been recruiting on the technical side, strengthening quite a lot. There have been quite a few new starters this year.
"There are also some, as yet, unannounced that will be headline grabbing when they are, so there are things going on."
Prodromou initially worked under Newey at McLaren from 2000-2005, and when the latter joined Red Bull he ensured the former followed.
Should Prodromou be confirmed at McLaren it would be the end of a partnership with Newey that has seen them work together for almost all of the last 13 years.