The teams remain locked together in mid-table in the Ladbrokes Premiership after a forgettable encounter which was lacking in meaningful incident apart from a brief flurry of chances either side of half-time.
Motherwell were without the injured Nadir Ciftci, Charles Dunne and Allan Campbell before their trip to Hampden to face Aberdeen, the latter two more as precautions, although the on-loan Celtic striker has a chance of overcoming an ankle injury.
Barry Maguire was handed a debut in a back three while midfielders Gael Bigirimana and Liam Grimshaw were handed chances to stake a claim for a semi-final appearance.
But there was little to catch the eye at McDiarmid Park.
Both sides had seen their top-six hopes evaporate in the previous week to leave them probably playing for seventh and eighth spot and a £60,000 difference in prize money.
The teams were tied on 37 points before the game and there was nothing between them in a first half that was devoid of noteworthy action until the final 10 seconds, when Saints midfielder Murray Davidson shot just wide from 22 yards after being found in space by Steven MacLean’s square pass.
There was more goalmouth action in the first four minutes of the second half than the whole of the opening period. Motherwell goalkeeper Trevor Carson held a free-kick from Greg Tanser before stopping David Wotherspoon’s volley.
Wotherspoon soon hit another free-kick wide and Curtis Main produced Motherwell’s first decent effort when he got away from Jason Kerr and curled just wide of the far post.
Main was substituted along with Elliott Frear in a clear sign Stephen Robinson had one eye on the semi-final, and the visiting manager handed Andy Rose a timely comeback from a knee injury in the 73rd minute as Maguire went off following an assured introduction to first-team football.
Bigirimana tried to make his mark with an ambitious effort from a free-kick which Alan Mannus spilled for a corner, before setting up Grimshaw with a brilliant piece of skill and a decent cross. But the former Preston midfielder’s last-minute effort was blocked in a crowded goalmouth.