It was a well merited win for Oldham against a disjointed Walsall side which generally struggled to make an impact and slumped to their fifth defeat.
Ricketts put Oldham into a commanding position with a 33rd goal and then earned a 64th minute penalty which was converted by Andy Liddell, who has never missed from the spot.
In the last minute Craig Davies completed Oldham's conclusive win with a goal carved out by Lee Hughes.
Oldham belied their lowly position after four successive defeats by producing a more skilful first-half display than an off-key Walsall outfit.
The shortcomings in Walsall's midfield were evident early in the game when Davies collected a long ball from Neal Eardley but let himself down badly with a weak shot which was easily handled by Clayton Ince.
Walsall's attack lacked fire or finishing power and the only time Mark Crossley was tested in the first half was when Ed Sonko fired in a hard cross shot which the much travelled goalkeeper coolly saved.
Oldham were a yard faster and took the lead when Liddell sent Ricketts clear down the right and, after controlling the ball, flashed his shot home for only his second goal of the season.
There was an immediate improvement in Walsall's play with the introduction of the talented Ishmel Demontagnac, who was always prepared to take on the Oldham defence.
Despite a further two substitutions, Walsall were unable to get back on level terms and the game was put out of their reach when Liddell converted his 65th minute spot-kick.