Fresh from his 10th title in Monte Carlo last week, the 'King of Clay' is on track to also take his tally at this ATP 1000 event into double figures.

Few would have foreseen the defending champion encountering many problems against his opponent, ranked 92nd in the world, but Chung went toe-to-toe with Nadal in the early stages and often came out on top.

The South Korean qualifier took a 3-1 lead in the first set but it was soon back on serve and, after Nadal saved a break point at 5-5, the Spaniard proved too good in the tie-break.

Unfortunately for Chung, the second set followed much the same pattern as the breaker, Nadal showcasing his class on the clay to cruise into the last four.

Nadal's strong finish was a far cry from his sloppy start, a backhand into the net giving Chung an early break, but Nadal hit back swiftly thanks to a superb passing forehand up the line.

That same shot served him well as he rescued a break point at a crucial juncture, and a remarkable reaction volley at the net in the breaker was evidence of his growing momentum.

Nadal maintained the pressure with a break to open the second set, before Chung committed a couple of unforced errors in game five to hand the Spaniard a commanding lead he would not relinquish.