Rahm, trying to win for the third time at home and join the great Seve Ballesteros for the most Spanish Open titles, was left just one stroke behind leaders Ashun Wu and Kiradech Aphibarnrat after Thursday's first day at Club de Campo Villa de Madrid.

"It's not that my heartbeat was faster, but it was definitely a lot more intense on the first few shots and putts just because I'm playing in front of the home crowd and I want to do good, and they want me to play well," smiled Rahm after a round featuring six birdies, an eagle and a bogey.

"It always helps when you start with a birdie, it always helps settle things down, and then getting a nice up-and-down on the second hole got me going.

"It's not that it's more nerve-wracking to play at home, but it just matters more, it's a little bit more intense."

Rahm finished in a tie for 17th last year when he was ranked World No.1 and had won the US Open and played well in the Ryder Cup.

China's Wu took the early lead after making eight birdies and no bogeys in a round of 63, the same score as Thailand's Aphibarnrat, who made five straight birdies after a bogey on the 12th.

Also a shot back were Swede Joakim Lagergren and Frenchman Matthieu Pavon.

Australian hope Min Woo Lee had a superb start, firing five birdies in the first eight holes but dropped a shot on the 16th to finish with a four-under 67, leaving him in joint-14th place.

Queensland's Maverick Antcliff was Australia's next best, having shot a two-under 69 to be tied for 31st, while Jason Scrivener was joint-69th after his level-par opener.

Defending champion Rafa Cabrera-Bello struggled and was tied for 108th after a 74.

Englishman Daniel Gavins had a memorable day, rebounding from a quadruple bogey on the par-4 8th with a hole-in-one on the short 9th.