Monte Carlo - Rafael Nadal offered a low-key appraisal on Monday of his chances for a record-extending 12th Monte Carlo Masters title as he prepares to return from his latest injury lay-off.

The 32-year-old Spaniard, whose bad knees and constant stoppages from competition have defined his career as king of clay, was extremely hesitant to even rate his chances as he gets set to face Roberto Bautista Agut in Wednesday's second round start.

"I cant give you any feeling, it's been a rough year and a half for me," Nadal said ahead of his first match since withdrawing hurt prior to an Indian Wells semi-final against Roger Federer last month.

"It's tough for me to get a clear view of how I am. It's all hard for me personally."

Nadal has a vast number of ranking points to defend on clay after lifting titles in a spectacular 2018 run at Monte Carlo, Barcelona, Rome and Roland Garros.

His only other trophy during a season in which he did not play at all after the US Open came on hardcourt in Toronto, where he beat young gun Stefanos Tsitsipas in the final.

Nadal is seeded second here behind Novak Djokovic, who is hoping to build for the French Open as he attempts to complete a personal sweep by winning his fourth straight Grand Slam title.

While Bautista Agut fought back to beat Australian John Millman 3-6, 6-1, 6-1, Denis Shapovalov's 20th birthday celebrations fell flat as he lost 5-7, 6-3, 6-1 to German Jan-Lennard Struff.

The 15th seed has yet to claim a win in the Principality after losing in the first round a year ago to Tsitsipas.

The nearly two-hour effort was marred by 10 double-faults from the Canadian youngster, who was broken six times.

Russian 10th seed Daniil Medvedev advanced easily over Portugal's Joao Sousa 6-1, 6-1, but Hungarian Marton Fucsovics dumped out Nikolaz Basilashvili, the 12th seed, 7-5, 3-6, 6-1.