The latest leg of the ATP Masters 1000 Series heads to Madrid with the perennial question - who can stop rampant Rafael Nadal on the surface he cherishes most of all?
The world No 1 has already claimed his 11th Monte Carlo title and followed up with an 11th success in Barcelona and he heads to Madrid where a victory in the final next Sunday would mean an 11th title in the event, having beaten Dominic Thiem in last year's final.
He will face either Gael Monfils or Nikoloz Basilashvili in the second round while Thiem and Juan Martin del Potro loom as the major threats in his half of the draw.
However, Nadal's dominance on the red dirt is astonishing - he is yet to drop a set, let alone lose a match, on clay since his defeat to Thiem in Rome last year, it's a winning streak that stands at 19 successive matches and 46 consecutive sets.
In between the Spaniard won his 10th French Open title at Roland Garros and has gone on to put a knee injury that threatened his early season behind him with his spectacular run with an 11th title in Paris the ultimate goal.
"I was patient and had the right attitude to try to get to the clay season as fit as possible," said Nadal.
"Coming into the clay season having played only four matches is not the ideal preparation, but to be honest, I feel that I've been playing well.
"They were difficult times. I feel like I've missed a lot of important opportunities in my career [because of injuries]. I counted all the majors in which I was not able to compete in normal conditions and there were a lot, to make it through it, you have to be patient."
As well as Nadal, the majority of the world's top 10 are in Madrid. Roger Federer's absence from the clay-court swing means Alexander Zverev is the second seed and a title in Germany on Sunday allied to his impressive Masters record make him the major danger.
The 21-year-old was a finalist in Miami and a semi-finalist in Monte Carlo, having picked up his first two Masters titles with victories in Rome and Toronto next year.
Zverev could face rising Greek star Stefanos Tsitsipas in the second round, if the 19-year-old gets the better of Evgeny Donskoy but the man they all have to beat is Nadal.
One to watch
Some weeks it is harder than others to pick our match to watch, not so in Madrid where two-time champion Novak Djokovic and Kei Nishikori meet in the stand out first-round match.
The pair are more used to semi-final and final meetings and have not met at this stage of a tournament since 2010, it's Djokovic who leads the head to head (11-2) with Nishikori without a win since 2014.
Djokovic's struggles are well documented, he has dropped to 12 in the world rankings after suffered an alarming run of disappointing defeats since coming back from his latest attempt to rectify his problematic elbow injury.
He flashed in Monte Carlo with a couple of victories before defeat to Thiem but he followed up with a loss to Martin Klizan in Barcelona and he will hope for the sort of inspiration that took him to the last four here last season.
Nishikori, a runner-up in Madrid in 2014, has also endured his fair share of injury problems like Djokovic, missing a large chunk of last season but a run to the Monte Carlo final, where he was beaten by Nadal, suggests he is getting back to his best.
Brit Watch
Kyle Edmund may have picked up a maiden ATP doubles title in Estoril on Sunday but his wait for a singles crown goes on after he suffered a quarter-final defeat last week.
The British No 1 has risen to a career-high 22 in the world rankings but he has been handed a tough opening assignment in Madrid, when he faces Russia's Daniil Medvedev.
The 22-year-old is a hugely capable performer on his day and won his maiden ATP title in Sydney earlier this year - form and fitness have prevented him making a major mark since, but Edmund will know the threat having come from a set down in Winston-Salem last year to win in three sets in their only meeting to date.
A win for Edmund means a second-round date with either Djokovic or Nishikori.
Surprise in Store
Let's stick our neck out and earmark Juan Martin del Potro for an early exit. The Argentine, champion in Indian Wells, can sometimes takes a little while to get going and Julien Benneteau or Damir Dzumhur could punish him - but we will take Richard Gasquet to beat him in the third round.
14th seed Tomas Berdych was the first big name to fall, going down to the in-form Frenchman when the tournament properly began on Sunday and while Del Potro is just as likely to reach the final it would be no surprise to see him fall early.
Jack Sock, seeded 12th, looks vulnerable against clay-court specialist Pablo Cuevas, although the Uruguayan has not been in the best of form while 15th seed Lucas Pouille could come unstuck against the talents of his fellow Frenchman Benoit Paire.
The Masters 1000 Series continues throughout next week with our coverage of the ATP Madrid Open getting underway on Sky Sports Arena on Monday from 11am.
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