Kei Nishikori returns to the Memphis Open looking for a third consecutive title at the indoor event, but faces a potentially difficult run to the final.

World number five Nishikori defeated Feliciano Lopez in 2013's showpiece, before repeating the feat 12 months ago against Ivo Karlovic.

Nishikori, runner-up at the US Open last year, starts as the clear favourite to make it a hat-trick of wins as the only top-10 ranked player competing in Memphis.

However, Nishikori - winner of four ATP events in 2014 - is sure to face stiff challenges along the way if he is to defend his title.

A repeat of last year's final is on the cards in the quarter-finals, with fifth seed Karlovic a potential opponent.

Home favourite John Isner, seeded third, is also on the same side of the draw as Nishikori and the big-serving American would await in the semi-finals, should he make it that far.

Isner has shown his ability to last the distance in Memphis in the past having reached the 2010 final, but he was on the receiving end of a three-sets defeat to compatriot Sam Querrey on that occasion.

On the other side of the draw, South Africa's Kevin Anderson " sitting at a career-high 15th in the world rankings - goes in search of a third career title having been handed a wildcard for the event.

Anderson (2), who reached the fourth round of last month's Australian Open before bowing out to Rafael Nadal, joins the other top four seeds in receiving a bye in the first round.

A quarter-final with American Steve Johnson (6) is a possibility, while fourth seed Alexandr Dolgopolov - who could face Anderson in the semis - will also have eyes on the top prize.

Others hoping to challenge in Memphis include Benjamin Becker, Adrian Mannarino, 2010 champion Querrey and the unpredictable Bernard Tomic.