Montoya will become a McLaren driver in 2005

The Colombian driver is switching to McLaren in 2005 and Brawn said it could create divisions at Williams if the 2004 championship was a close race.

"It's a little unfortunate. It's going to be a difficult year for Montoya and the people around him," said Brawn.

"A lot will depend on how competitive Williams are and the competition between their two drivers."

Brawn told BBC Radio FiveLive: "If Williams are extremely competitive and run away with the championship Juan Pablo could get on well.

"But if it's a tense championship and there's tension between the two drivers [Montoya and Ralf Schumacher] it's hard to see the situation not surfacing frequently."

Brawn continued: "When Michael Schumacher announced he was leaving Benetton to join Ferrari things were not so easy.

"You wonder where his mind is - is his mind on the future, or on now?

"And you can't build things because you're not building with him for the future."

Brawn returns to work with Ferrari on 5 January for a week's testing in Jerez.

But six-time world champion Michael Schumacher will not get back into the car until the third week of January.