Defeat at the hands of Dundee - combined with Dundee United's own last-gasp victory over Aberdeen - saw Killie fail to book their place in the top six ahead of the league split.
Every team who did make the cut - other than champions in waiting Celtic - are now vying for a European spot.
But, despite their own ambitions being limited to seventh place at best, McKenzie insists Kilmarnock's players will be motivated for the visit of Hearts.
The forward said: "It was a tough few days after the game against Dundee but we've had a break since then. It's not forgotten about but we are just focusing on the Hearts game now.
"A lot of people are saying there is nothing to play for but I don't see it that way at all.
"We've got players playing for contracts and there is still a lot of money to play for in terms of places in the bottom six. So I see the game against Hearts as a big game."
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