Jamie Paterson's strike gave the Saddlers a first half lead but an eventful second 45 minutes saw saw Jordan Stewart handed an early bath for a second bookable offence with Craig Westcarr bagging a brace for the hosts, one from the spot, and one more from Paterson late on to hand Walsall all three points.
City boss Steven Pressley decided not to tinker with a winning formula for the clash, naming an unchanged line up following the Sky Blues' 1-0 home win over Doncaster Rovers on Good Friday.
Walsall came out of the blocks quickly though and matched City for endeavour, even getting to the byline after seven minutes when Westcarr flashed a dangerous ball low across the six-yard box.
A well worked free kick from the Saddlers then opened up a lane for Paterson to have a shot from 20 yards which Joe Murphy saved comfortably.
The home side's early efforts though should not have detract from the Sky Blues early skirmishes though when, on 22 minutes, a deep cross from Cyrus Christie picked out William Edjenguele at the back post to head just over the bar.
The was a mild scare for City at the back though a minute after the half hour when Adam Barton lost possession in the midfield to Paterson whose lofted ball then searched for Febian Brandy although Murphy was on hand to tip the bouncing delivery into the path of the recovering Aaron Martin.
Walsall got the opener just a minute later through Paterson when he picked up the ball just inside the area and jinked his way past two defenders before sliding the ball across Murphy and into the far bottom corner.
The goal did not seem to phase City though who stuck to their task and were almost rewarded when Franck Moussa's 25-yard effort was turned around the post by Sam Johnstone.
The Sky Blues were unlucky from the resulting corner as well when John Fleck's delivery got a glancing head off Carl Baker and bounced off the head of Ball as it drifted wide.
Baker and Ball nearly linked up again on 39 minutes when Baker broke down the right and fired from the corner of the area, Johnstone spilling the ball into the path of Ball who did not have time to react and stabbed wide.
Walsall went close to a second though two minutes before the break when Paul Downing flashed a waist height cross across City's six yard area which Stewart had to flick away with his heel.
The Sky Blues came out firing after the break and nearly got a leveller but for a great save from Johnstone when Christie swung in a cross for Baker whose close range header was tipped over the bar by the Walsall 'keeper.
It was the hosts who grabbed the next goal though on 53 minutes courtesy of Westcarr's spot kick.
Martin's poor touch in the area allowed James Baxendale to nick the ball off his boot, Martin stretching to recover and bringing the midfielder down in the area, Westcarr then converting cooly and sending Murphy the wrong way.
City were then given a mountain to climb after the hour when Stewart was given his marching orders for a challenge on Brandy which saw him pick up a second yellow card.
It then got worse for the Sky Blues with 17 minutes to go when substitute Steven Jennings was penalised for a challenge on Brandy, Paterson's free kick parried by Murphy but only into the path of Westcarr who was left with a simple tap home to make it 3-0.
The travelling City fans' misery was then compounded with three minutes to go when Westcarr ran at the Sky Blues back four and slipped in Paterson to slot home his second of the afternoon and complete the scoring.
Attendance: 7,504 (2,459 Sky Blue Army)
Coventry City: Murphy (GK), Christie, Edjenguele, Martin, wartSte, Bailey, Barton (Jennings 65), Fleck, Baker (c), Moussa (J Clarke 65), Ball (Wilson 62)
Subs: Dunn (GK), Bell, McSheffrey, McDonald
Walsall: Johnstone, Butler (c), Chambers, Paterson, Brandy (Hemmings 87), Downing, Baxendale (Sawyers 87), Chambers, Taylor, Mantom, Westcarr
Subs: Roberts (GK), Holden, Featherstone, Purkiss, Benning