Walsall battled bravely after having goalkeeper James Walker sent off in the 30th minute.
They were then leading by goals from Jorge Leitao and Junior but afterwards were fighting an uphill battle, despite Zigor Aranalde giving them a 3-1 interval lead with a 44th minute penalty.
Preston, however, hit back after David Healy reduced the arrears in the 38th minute. Skipper Chris Lucketti and Alexander salvaged a point with goals in the75th and 88th minutes.
The Saddlers carved out the best chance in the opening 15 minutes when Darren Wrack shot wide after the ball bounced into his path off Marlon Broomes.
For a spell the game developed into a tight struggle with Preston, the draw specialists, dropping a defensive blanket on Walsall's attacks but they fell victim of their own tactics.
Junior, Walsall's Brazilian striker, produced a low shot which hit a Preston defender and trickled a few yards into the path of Leitao to put the Saddlers ahead.
The highlight of the game occurred in the 26th minute when Junior stamped his mark on the game with a spectacular goal.
He collected a pass from skipper Martin O'Connor and raced 20 yards before cutting inside to score with a curling shot from 25 yards which roared into the top corner of the of the net to the right of Tepi Moilanen.
Four minutes later the whole complexion of the game changed when Walsall's goalkeeper Walker was sent off for handling outside the area following a tackle on Richard Cresswell.
Walsall took off Junior to enable them to send on goalkeeper Gavin Ward. He was quickly in action saving from Healy, but the little Preston striker reduced the arrears with a headed goal in the 38th minute.
Preston went in search of the equaliser but a minute before half time Eric Skora handled a left-wing cross to concede a penalty which was converted by Aranalde with a shot which cannoned off Miolanen and into the net.
Although down to ten men Walsall battled to retain their advantage but they could not hold out.
Lucketti headed home a left-wing cross in the 75th minute and in a hectic finish Alexander was on hand to push home a left-wing cross from Iain Anderson.