McAlister, the former All Black centre who arrived at Edgeley Park on a lucrative two-year contract after last year's World Cup, was deployed at fly-half with Charlie Hodgson on the bench following the birth of his first child.
McAlister, 24, provided Sale with significant attacking impetus in a comfortable six-try victory and dovetailed effectively with England scrum-half Richard Wigglesworth.
Sale will now face a semi-final trip to either Bath or Leeds on April 26, and winning the competition will secure them a place in next season's Heineken Cup.
That McAlister has not always lived up to his reputation since joining Sale is undeniable - and even here his tactical kicking game was up not to Hodgson's lofty standards - but he still landed 19 points with the boot and provided a delightful crossfield kick which allowed Lee Thomas to touch down in the first half.
McAlister spent part of his childhood in Oldham, where his father Charlie was a legend at the town's rugby league club, and played in the junior ranks at Manchester United.
Saint-Andre said: "We rested Charlie but Luke showed what a good footballer he is and everybody knows that.
"It was good to see him at fly-half - he showed a lot of class and is starting to gel more and more in the team."
It was McAlister's handling skills which helped guide Sale around the field to open up a 21-12 interval advantage with tries from Sebastien Chabal and Thomas.
The Sharks added further scores after the restart through Juan Martin Fernandez Lobbe (two), youngster Will Cliff's first try for the club and a penalty try which McAlister converted.
Brive proved spirit opponents and scored four tries of their own through Farid Sid, Jean-Phillipe Bonrepaux and Vickus Liebenberg.
But Sale were simply too strong.
"We're in the semi-finals of the competition and are still in contention in the Guinness Premiership," added Saint-Andre, whose side also remain well-placed in the league for a play-off berth ahead of forthcoming trips to Bristol and Wasps.
"It will be a big race in the Premiership but we're only a few points off the top and that's much better than at this stage last season."
The only negative for Sale was a leg injury which forced Chabal off in the second half but Saint-Andre hoped it was not serious.