Rafael Nadal will look to return to winning ways when he heads the field at the Mercedes Cup, which gets under way on Monday.

The Spaniard suffered a rare disappointment at the French Open this week, losing out in the quarter-finals to Novak Djokovic.

It was only Nadal's second ever defeat at Roland Garros, after nine titles in the previous 10 years on the clay in Paris.

He was a long way from his best as a dominant Djokovic romped to a straight-sets victory, and defeat will see Nadal drop to 10th in the rankings as a result - his lowest position since April 2005.

With the third grand slam of the year at Wimbledon just three weeks away, Nadal now switches to the grass in preparation for a tilt at a 15th major title.

His build-up begins at this ATP 250 event in Stuttgart, where he has previously triumphed twice, in 2005 and 2007, although both of those victories came on clay.

This year's tournament marks the first time it has been held on grass, with Roberto Bautista Agut the victor in 2014 with a 6-3 4-6 6-2 success over Lukas Rosol.

"I am very happy to play again in the city of Stuttgart," Nadal said when his participation in the event was announced.

"Last time I played there it was a different event, on clay. This time it will be on grass court and I'm really looking forward to return to Stuttgart. It's great to be back playing soon in Germany."

Neither Bautista Agut or Rosol are present at this year's tournament, while Nadal's likeliest challengers will be fellow top-four seeds Marin Cilic, Feliciano Lopez and Gael Monfils.

Frenchman Monfils retired when a set down in the 2010 final against Albert Montanes, while another former runner-up, Philipp Kohlschreiber will be hoping to go one better than his defeat to Fabio Fognini in the showpiece two years ago.

Kohlschreiber will likely represent the best chance of a home victory, although Tommy Haas will be hopeful of a strong run after over a year out with a shoulder problem.

"Of course I am happy to go back and play before a German audience because I do not know precisely how often something like this can happen again," the veteran said.

Haas reached the final back in 1999 but, after taking a two-set lead, crumbled and lost 6-7 (6-8) 4-6 7-6 (9-7) 6-0 6-3 to Magnus Norman.