Morton had to make late adjustments to their original line-up because of a bout of food poisoning among the squad but, although the replacements performed creditably, there was no excuse for the lack of entertainment for the 3,000 spectators.
'Ton's Jim McAlistair was the first to deliver a shot after eight minutes, but his effort from 25 yards sailed into the crowd.
Jason Walker had another chance when a Ryan Harding through ball bounced awkwardly off Sandy Hodge into his path, but he hurried his angled drive past Kenny Arthur's left-hand post.
Thistle offered nothing in attack and there were long tedious spells for the crowd to endure as passes went astray, but Walker's near-post header from Scott McLaughlin's corner forced Arthur to save the ball between his legs right on the line.
Darren Brady volleyed a Mark Roberts cross high over the crossbar in a rare Thistle attack, and Willie Gibson was denied by a fine Dean Keenan tackle just after the break.
The second half soon degenerated into the same dire fare as the first and more excitement was created by a flock of squabbling seagulls brawling over a morsel of bread just in front of the Cowshed.
Remarkably, the only goal was cleverly fashioned. Chris Millar collected a diagonal pass at the junction of the goal-line and six-yard box and confused the Thistle rearguard with a deft back-heeled pass across the goalmouth where Walker met the ball to slam it past Arthur.