Dustin Johnson admits it will be 'tough' to retain his world No.1 status throughout the year but he insists he's up for the challenge.

Johnson fighting to stay No.1

Johnson fighting to stay No.1

Johnson has been top of the rankings since last February but his position is under threat this weekend from No.2 Jon Rahm, with the Spaniard bidding to usurp him if he wins the AT&T Pebble Beach Pro-Am.

Johnson will hope he can reclaim the Pebble Beach title that he won in consecutive years in 2009 and 2010 on Sunday to stay on top of the rankings but he's well aware of the talented chasing back breathing down his neck if he slips up.

He said: 'If I keep playing well and keep winning then I'm going to stay number one. If I don't play well, there's a lot of really good players that are playing really well right now.

'So it's going to be tough for me to keep it, but if I keep playing like I am and how I should, then, yeah, I'll be there at the end of the year.'

Johnson was third in the AT&T Pebble Beach Pro-Am last year and he admits he relishes the tournament, which is played over three courses - Pebble Beach, Spyglass Hill and Monterey Peninsula.

He added: 'I just really enjoy coming here. I enjoy the courses, they're a lot of fun to play.'

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