Having come through East qualifying the Paties Road outfit have been drawn away to holders Giffnock in Saturday's first national round of the competition.
"It's a tough draw but we hope to build a decent team around Steven McGuckin, Neil McPhee and myself," said Thistle skipper Alan MacDonald.
St Serfs find themselves badly hit by call-offs for their home clash with Braid at Clark Road when they will be hoping to repeat Monday's 10-2 league win over the same opponents.
Coaching commitments down south rule out Neil Harden and Dave McLean while Matt Davies, a qualified umpire, will be officiating elsewhere.
And the Gaffney brothers, Mark and Dave, are ruled out leaving St Serfs hopes in the hands of Frenchman Vincent Hivert, second team captain Fraser Gray, new recruit Michael Blair, secretary Richard Miller, former club singles finalist Ewen Pendreigh and the long serving Michael Notman.
Braid will also be below full strength on Saturday with Andy Moffat and Allan Ralston cup-tied for, respectively, Montrose and Newlands.