De Los Santos stumbled with three bogeys against two birdies to trail new leader Cameron Smith of Australia by 13 strokes.
The Filipino has a two-round total of 144 at joint 66th following a first-round 71.
De Los Santos struggled with early bogeys on the second and fifth before rising to the challenge with a birdie on the seventh.
He tripped with another bogey on the par-4 13th hole before making up with a birdie 4 on the 14th.
Meanwhile, Smith grabbed the lead from American Cameron Young after shooting a bogey-free 64 for 131. He had an earlier round of 67.
Young trailed by two strokes at second after a 69 for 133, while Rory McIlroy came in third with a 68 for 134.
Tiger Woods missed the cut after struggling with a 75 for 153.
Credit belongs to : www.mb.com.ph