The Bairns head to Stark's Park on the back of a disappointing couple of weeks after a defeat to Clyde and draw with Airdrieonians in League One.
However, morale hasn't been dented within the squad and Longridge, who played for Raith under McKinnon, insisted the Challenge Cup encounter is an ideal game to kick start their campaign.
He told the Falkirk Herald: "Obviously, the last couple of weeks we haven't got the results we have been wanting.
"We're under no illusions it is a tough league and I knew that when I signed. The manager has tried a few things and that's us now got the wake-up call we need.
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"We've got to grips with the league now and we know what is required.
"It should be a good game, it's a wee break from the league. We've got Raith in the league soon, so hopefully we can put down a good marker, go there and get a positive result and show that we're not here to mess about."
Longridge believes the Challenge Cup is one they should be aiming to win. The Bairns are the record holders in the competition with four wins under their belts - the last coming back in 2012.
He said: "Yeah I think especially with this cup, a cup run is important.
"The Scottish Cup has the big guns in it and it's very difficult - you're just hoping to get a good run and good home tie against a Celtic or Rangers for the club to benefit financially.
"But this cup, if you look at the squad we've got and the teams that are in it, we've got a real good chance to progress and I think every team in the lower leagues will think the same."
Longridge is familiar with the Raith squad having played there a couple of seasons ago but he stressed there will be no room for sentimentality come kick off.
He said: "I know a couple of players like Kieran MacDonald who has just signed from Airdrie.
"You have the laugh and the jokes before but I think once the game starts that's it, you're in the zone, you're there to perform, and hopefully come away knowing you're into the next round."