New York, Sep 14 (DPA) Rafael Nadal leaves New York set for medical tests at home in Spain to determine the extent of the abdominal muscle problem that has plagued him for a month.

The Spaniard, who returns to second in the world next week, revealed Sunday after losing his US Open semi-final 6-2, 6-2, 6-2 to Juan Del Potro that pain from the problem has gotten worse.

After deciding to play through the Open no matter what, the six-time Grand Slam champion will now take the time to see what is actually wrong.

'I have to see the doctor in Spain and do another test, because I didn't want to do a test during the tournament because, anyway, I gonna play. So I don't know how is the injury right now, but I expect not a lot.'

Nadal withdrew from Spain's Davis Cup semi-final next week in Murcia on clay against Israel, but is due to play for the first time at the Bangkok Open starting in a fortnight.

The Spaniard said he picked up the problem a month ago in Montreal, where he returned after two months out resting tendinitis-plagued knees.