Stevie May's 20th goal of the season against Partick handed St Johnstone just their second Scottish Premiership win outside of Perth this season.
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The Scotland Under-21 international netted from eight yards after 27 minutes, finishing off some terrific work by David Wotherspoon to confirm a 1-0 win at Firhill.
Saints dominated the first half before Thistle responded with spirited display after the break.
But the Jags lacked the quality of final ball to really trouble Saints and Tommy Wright's men clung on to claim the win which took them to within a point of fifth-placed Dundee United.
The match - rearranged after the original fixture on December 14 was abandoned due to a waterlogged pitch - pitted a Partick side yet to win at home league fixture against a Saints line-up whose only previous away win outside of cup duty came against the whipping boys of Hearts three months ago.
Wright named Steven Anderson in his line-up side after appealing the defender's weekend sending-off against Hearts.
But goalkeeper Alan Mannus had to accept his punishment following the dismissal he received for clashing with the Jambos' Ryan Stevenson, as his place was taken by 41-year-old Steve Banks.
Jags boss Alan Archibald also had suspension concerns with Aaron Taylor-Sinclair - sent off against Kilmarnock on Saturday - and Stuart Bannigan both banned, meaning Jordan McMillan was joined in the Thistle starting line-up by the returning Chris Erskine following his loan move back to Firhill from Dundee United.
But May's goal just before the half-hour mark after Wotherspoon slammed into the box proved to be enough to claim the points as Thistle missed out on the chance to climb out of the relegation play-off spot.
Both sides held little back in the opening stages but it was the visitors who were first to threaten as Lee Croft teed up Stevie May to shoot from 10 yards out, only for Thistle midfielder James Craigen to block bravely.
Saints' Gary McDonald had the ball in the net after 11 minutes, finishing well from Chris Millar's ball in behind the Jags' defence only to be flagged for offside as he turned to celebrate, while Paul Gallacher produced a solid save from Paddy Cregg - deputising for Murray Davidson after the Scotland international was ruled out for the season with a knee injury - seconds later.
The Perth men were looking the more likely to score as they eagerly pressed forward but the combined ball skills of Erskine and Kallum Higginbotham offered Partick hope on the counter.
But Thistle could only hold out so long as St Johnstone's pressure finally told.
Wotherspoon made a fool of right-back Stephen O'Donnell as he skipped past before beating Lee Mair and Conrad Balatoni. The former Hibernian man looked set to shoot himself only to shift the ball square for May to net his fifth goal in three games.
Higginbotham swept a free-kick from a tight angle just past the far post as Thistle sought an immediate response. Only an impressive diving save from Banks prevented Lyle Taylor from going one better on 35 minutes as the striker smashed a 30-yard set-piece towards the bottom corner.
Thistle looked a team re-energised at the start of the second period and could have levelled after Higginbotham's cross was stabbed into the ground by Taylor before the strike bounced over Banks' bar.
They almost got lucky when Lee Mair's pass took a deflection off a Saints foot before nearly wrong-footing Banks. On the other hand, O'Donnell's mistake went unpunished after his stray pass fell to May, who shot straight at Gallacher.
Archibald's patience with his shot-shy team was growing thin and he threw on a second striker in the shape of Kris Doolan in a bid to spice up their attack. But too many rushed passes or mistimed shots made it easy for the visitors to clear.
When Thistle did keep their composure, Erskine could only fire wide on 80 minutes while Doolan sent a low shot across the face of goal after decent work by O'Donnell down the right five minutes later.
After that, it was down to Tam Scobbie's 89th-minute block on substitute Ross Forbes shot to preserve the result for Saints.