Championship leader Nico Rosberg believes that Red Bull racer Daniel Ricciardo is a genuine threat in the 2014 title race.
Rosberg's collision with Mercedes team-mate Lewis Hamilton at the Belgian Grand Prix cleared the way for Ricciardo to collect his third win of the campaign and close to within 64 points of Rosberg.
The German believes that he needs to be wary of his rival ahead of this weekend's Italian Grand Prix.
"Ricciardo's win in Belgium saw him close the gap to Lewis and I in the drivers' standings," Rosberg wrote in his Sportsmail column.
"He is doing a great job this season and he is a serious rival for title so we must keep a close eye on him and Red Bull in the remaining six races."
Rosberg also commented on the decision to replace part of the gravel run-off at the Parabolica corner at Monza with tarmac.
"This year they have changed the run-off area at the world-famous Parabolica corner in Monza, replacing the gravel trap with Tarmac," he said.
"I haven't seen it yet, but I notice that it has attracted some criticism from the sport's fans.
"I completely understand that and it is a pity because it makes it easier for the drivers when there is room for error. But safety has to be the priority, and that is why they've brought in the change."