The Lancashire side owed a large debt of gratitude to goalkeeper Carlo Nash who produced a hat-trick of fine saves to keep the Saints at bay.
The former Manchester City shot-stopper somehow clawed out Grzegorz Rasiak's header in the 26th minute when the Pole seemed certain to score from five yards out.
Ten minutes later Nash flung himself to keep out Andrew Surman's free-kick.
The Lilywhites keeper then further frustrated the St Mary's faithful when he saved with his feet to deny Rasiak once more in the second half.
At the other end, David Nugent was guilty of mis-firing on two occasions. The much sought after striker bungled chances on 15 and 68 minutes to keep the score level.
Nugent blasted over from eight yards in the first half after former Saint Brett Ormerod crept in at the far post to head downward.
Nugent's second miss came as part of a three-minute second-half spell in which the away side missed three gilt-edged chances.
Defender Youl Mawene found room inside the six-yard box to turn and unleash a powerful effort that forced Bartosz Bialkowski into a smart save.
From the resulting corner Mawene headed Callum Davidson's delivery wide when he was unmarked at the far post.
Nugent then further infuriated manager Davies when he was the lucky recipient of a mis-hit Paul McKenna cross and his snap-shot flew well wide from 12 yards.
The impressive Richard Chaplow nearly won it for the relegation-threatened Saints 15 minutes from time when his sweetly struck 20-yard volley beat Nash for the first time, but cruelly rebounded to safety off the post.