Kyle Bartley’s goal, his first in a Light Blue jersey, on 24 minutes was enough to secure a crucial victory and it was a great moment for the Arsenal youngster who got on the end of a teasing cross from Madjid Bougherra.
Rangers’ injury problems were highlighted before kick-off with Smith naming just five outfield substitutes.
Under-19 striker Kane Hemmings was drafted in as was Darren Cole who played for Billy Kirkwood’s team in their 4-1 league win over Hibs yesterday,
They were joined by Salim Kerkar, who has yet to play for the top team, Kyle Hutton and Gregg Wylde.
The visitor’s made a positive start to the 90 minutes with the midfield five enjoying plenty of possession and Healy and Diouf making good runs up top.
After just seven minutes this strike pairing combined well with Diouf pushing forward with intent before feeding the ball to his Northern Irish teammate.
He cut inside but his curling effort from 20 yards was well saved by Paul Gallacher who dived to his left.
At the other end Thomson found space on the right and his teasing back post cross found Higdon but his poor touch put an end to a promising passage of play for the Saints.
The bobbly surface did little to help the teams but having got though the opening 15 minutes unscathed Danny Lennon’s men started to grow in confidence.
Van Zanten was pushing further up the pitch and his teasing cross from the right had to be palmed out of play my McGregor at full stretch.
From the resulting corner Lee Mair’s header from 12 yards had to be booted off the goal line nervously by John Fleck.
Rangers then went up the park and opened the scoring after Steven Davis had seen an excellent free kick palmed over the cross bar by Gallacher.
Diouf’s corner was cleared out for a throw-in which the Senegalese forward took quickly to Bougherra.
Madjid then hooked in a delightful cross to Bartley who calmly headed home his first goal in a Light Blue jersey.
After going behind St Mirren still looked a threat and another dangerous van Zanten cross was volleyed over by Kenny McLean inside the 18-yard box.
It was a great chance for the Saints’ no. 45 who might have been better sticking his head on the ball as opposed to trying an ambitious right-foot shot.
With seven minutes of the first-half left Edu had an opportunity to double his side’s advantage but his long range drive flew over Gallacher’s bar.
Paul McGowan then tried his luck from a similar distance but his effort curled harmlessly away from McGregor’s goal.
In to the second half and St Mirren almost got back in to the game when Kenny McLean spotted Paul McGowan in space at the back post but after floating a great corner to the winger his volley was wasteful.
Fleck then delivered an accurate corner in to the Saints 18-yard box and Edu smashed his volley in to the away end of the ground.
After that Rangers struggled to build momentum with the Saints’ backline working hard to deny Diouf and Healy space and time on the ball.
With just over 15 minutes left Smith elected to make a double substitution with Hutton and Wylde replacing Healy and Fleck.
And immediately Wylde was in the thick of the action.
The youngster played a neat pass in to the path of Davis who then found Edu in space down the left channel.
The Rangers fans held their breath as the American powered in to the box but he skewed his effort wide of the far post.
As the clocked ticked down man-of-the-match Davis was unlucky with a dipping effort which almost caught out Gallacher who watched the ball closely as it narrowly missed his cross bar.
The home side threw everyone forward with injury time looming and van Zanten had the home support out of their seats when he darted forward and launched a low shot which flew across the face of McGregor’s goal.
This was to be the last chance for the Saints and Rangers held on to what could be a crucial victory come the end of the campaign.