Juan Martin del Potro and Roger Federer
Del Potro could be the greatest threat to Federer's title. Getty Images

Roger Federer's main threats at the BNP Paribas Open in Indian Wells come in the form of Juan Martin del Potro and Kevin Anderson, according to Mark Petchy.

The Swiss makes his first competitive appearance since winning the Rotterdam Open last month, where he also became the oldest world number one in tennis history, but Rafael Nadal will not compete after withdrawing due to a hip injury.

Federer will look to protect that ranking and defend the first half of the Sunshine Double he won last year when he travels to California to resume his 2018 campaign.

And Petchy, a former coach of Andy Murray, feels the 20-time grand slam champion is once again the man to beat in North America.

"If Roger puts his best tennis out there, he is the best player," he told Sky Sports. "He is playing with such utter freedom right now. He has got nothing to prove in terms of winning titles.

"This is all about his love of the sport which is clearly unconditional. He doesn't need to rewrite another chapter in terms of his legacy - that has been done in the last 15 months. He is not only winning slams, but is now back at world number one.

"When he plays the way he has done recently it is a pretty tough combination for the other players on tour to face right now. For him, it is almost an irresistible situation. Just go out there and play with house money."

While Federer was taking a week off to spend time with his family – he skipped the Dubai Duty Free Tennis Championships as a result – the ATP season continued apace with events in Mexico and the United Arab Emirates.

Roberto Bautista-Agut beat Lucas Pouille to claim the title in Dubai in Federer's absence, while Del Potro and Anderson contested the final in Acapulco – which saw the former US Open champion prevailing in straight sets.

And Petchy feels both Del Potro and Anderson are strong contenders when the tournament gets under way on Thursday (8 March).

"Del Potro has beaten Roger in the final of a major [US Open 2009] and is clearly playing with confidence," the ex-British Davis Cup captain added. "He is back in the top 10 which is always crucial when you are taking on somebody like Roger.

"The great thing about Del Potro right now is his backhand - because of all the wrist injuries that he has had. We have seen significant tactical changes in terms of hitting over it and also using the slice.

"His backhand now is arguably more versatile than it was when he won the US Open. It is probably helping him at this stage of his career to become a better player.

"Mentally, he has the belief that when he plays the big players he is capable of beating them. There are not many out there that have been allowed that particular strength. That is a crucial element."

On South African Anderson, last year's runner-up at Flushing Meadows, Petchy gleamed: "He has such a big game because he returns hard - on his bad days he doesn't make enough returns, but the majority of time you feel under pressure even when you are serving against him because he is taking such a big swing at the return that you don't get too much respite and rhythm.

"His serve is also one of the best out there. You have got to have something pretty special when you go out on court against Roger - otherwise you are not going to stand a chance and those two players right now certainly have enough in their game and confidence to take him on if they were to meet."