The Spaniard netted his 18th goal of the season in the 41st minute from the penalty spot - and it proved enough to stretch the visitors' unbeaten league run to six games.
Only the woodwork prevented Caley Thistle substitute Claude Gnakpa earning his team a draw in the third minute of injury time.
A far from meaningless game, this rearranged fixture from snowy January 2, gave both teams an opportunity to climb the table.
St Johnstone strengthened their bid for European football next season by leapfrogging Dundee United, while Inverness missed the chance to rise above Aberdeen and St Mirren into eighth.
Both managers made one change to their winning sides from the weekend.
Thomas Piermayr replaced Josh Meekings, who was suspended for a red card in Caley Thistle's 1-0 win at Aberdeen on Saturday. Northern Ireland goalkeeper Jonny Tuffey retained his place for the hosts, with Ryan Esson ruled out by a groin injury.
St Johnstone midfielder Murray Davidson missed out due to a knee injury, after scoring in their 2-1 win at home to Hearts on Saturday, and was replaced by Chris Millar.
Caley Thistle top scorer Gregory Tade - who netted the winner at Pittodrie - was first to test keeper Alan Mannus when he connected with a long ball from Piermayr.
It was a rare opportunity in an opening 15 minutes of few chances.
The Frenchman then fluffed his lines when the ball broke to him, after Billy McKay's effort was blocked by Mannus, and he fired wide.
McKay was thwarted by Mannus moments later when his low shot was blocked and the stopper pounced on his own spillage.
The visitors created their first chance midway through the half when Liam Craig headed a David Mackay cross a couple of yards wide.
Inverness manager Terry Butcher left his seat in the stand on the half-hour mark in a bid to encourage his team from the touchline.
Ross Tokely's header from a Greg Tansey free-kick was saved well by Mannus - and moments later Sandaza made Caley Thistle pay for their missed chances.
Tade barged into Craig and referee Willie Collum wasted little time in awarding the penalty, which was despatched with aplomb by the Perth side's top scorer.
The sides returned after the interval fired up but Collum calmed things down by distributing early yellow cards to Sandaza and Caley Thistle's Owain Tudur Jones.
Sandaza might have doubled the lead after a rampaging run down the right but his angled effort went inches wide, evading his onrushing strike partner Cillian Sheridan.
Caley Thistle hit back with captain Richie Foran's header flying just over the bar.
It was a rare chance as the game descended into a scrappy midfield battle.
Tade was the first to be substituted with a little more than 15 minutes to go, Nick Ross coming on as Inverness hunted a leveller.
Home fans were on their feet in 79 minutes thinking McKay had equalised but his low shot from 12 yards hit the stanchion behind the goal before rippling the net.
At the opposite end Tuffey produced a terrific diving save to deny Sandaza a second in the closing stages.
Inverness could have snatched a last-gasp equaliser but Mannus snatched a Gnakpa cross off Foran's head before the French attacker hit the top of the bar from 15 yards seconds later.