Fresh from winning the WGC Cadillac Championship on Sunday, Dustin Johnson has thrown the gauntlet down at Rory McIlroy's feet and declared that he's "not afraid" to challenge the world No 1.

Johnson came from five shots behind on the final day at Doral to win his ninth PGA Tour title in just his fifth event back after a six-month absence from the game to deal with "personal challenges."

The 30-year-old has yet to make his breakthrough in the majors but, having propelled himself back into the world's top-10, the American believes he is ready to step up to the plate and lead the challengers to McIlroy's throne.

"Clearly, Rory is a really great player and has won a couple of majors now but then I think I can play with him," he said. "I'm not afraid of him, that's for sure. He's a great golfer and I think I am too, so I would really like to have the chance to come down the stretch with him and see what we're both made of. He and I are really good friends and it would be fun to take him on. I know I'm up for the challenge."

Meanwhile, Glasgow's Marc Warren still has Georgia on his mind after a top-20 finish in the Cadillac event inched him tantalisingly close to a place in next month's Masters at Augusta.

Warren shared 17th spot in Florida at the weekend and has moved to a career high of 51st on the global rankings with the top 50 at the cut-off point the week before the Masters gaining instant access to the first major of the season.

Warren still has three weeks to achieve that ambition of a debut in the Masters and he was staying on in the US to try and qualify for this week's Valspar Championship.

Gate-crashing the world's top-50 would really open up the doors of opportunity for the three-time European Tour winner and getting the chance to make inroads on the lucrative PGA circuit is very much in his plans.

"To be No. 51 in the world is great but it's the bigger picture as those in the top-50 really can get to pick and choose where they can play," said Warren, who ended a seven-year title drought on the European Tour last season when he won in Denmark. "Being in Doral last week is what I have been working to achieve in my career so that these WGC events and the majors become more of a regular occurrence. It is a natural progression for me.

Warren is the second highest Scot on the world rankings behind Stephen Gallacher , who is now 36th.