The Saddlers were always the better side in a game that turned the League One table on its head.
Pool slumped to their worst form of the season as Walsall hit their best, and once the visitors had taken the lead, the result was never in doubt.
Former Villa star Julian Joachim, on loan from Leeds, set up the victory with a great opening in which he made one goal and scored a second.
Even after he limped off injured, Walsall stayed in command.
His first contribution came on ten minutes when he crossed low after a left-wing run and defender Matty Robson deflected the ball into his own net at the near post.
Four minutes later Joachim did the trick himself, scoring with a brilliant shot from the right of the area after his run took him from left to right across the face of the area.
Pool were shell-shocked and Walsall were in no mood to let them off the hook even after Joachim limped off.
On 42 minutes it was 3-0 when substitute Matt Fryatt sent Andrew Surman surging through the middle to slot in a third.
In the second half, Pool tried to battle back but the Saddlers kept control and the only consolation for the home team came too late to make any difference.
It was on 77 minutes when Robson was tripped in the area by Craig Pead and Adam Boyd blasted his 27th goal of the season from the spot.
It gave them some hope but they weren't up to a full fight-back and their play-off hopes now rest on their visit to Bournemouth on the last day, while Walsall must be early favourites to do well in League One next season.