McLaren's Jenson Button said Ferrari may have inadvertently given a boost to their rivals by re-hiring former world champion Kimi Raikkonen to join current lead driver Fernando Alonso.
Button, speaking ahead of Sunday's Singapore Grand Prix, said the decision was "great for us" and predicted difficulties at Ferrari as next season progresses.
The 33-year-old Briton said rather than being a dream pairing, two-time world champion Alonso and "Iceman" Raikkonen, who won the 2007 title with Ferrari, may find it difficult to cooperate.
"We'll definitely be watching their situation," Button told AFP.
"Ferrari for many years has had two drivers in the team that have been very quick but when it gets to a point in the season, it seems one driver helps the other driver.
"I don't think that will be the case with Kimi and Fernando -- I don't think they'll be trying to help the other driver. A guy that's achieved what they've achieved will not want to be helping out his team-mate."
Seven-time world champion Michael Schumacher has warned that the partnership could be "explosive", while Red Bull advisor Helmut Marko reportedly said the strong-willed duo could tear the team apart.
