The Ayrshire side defied the odds to knock out favourites Inverness and book their place in the quarter-finals of the cup competition with an impressive 2-0 win last week.
Sissoko sees no reason why Killie cannot build on the result and force their way into the top half of the table this term.
Kilmarnock head into their weekend match against Motherwell just three points behind sixth-placed Aberdeen and Sissoko says the dressing room is full of confidence.
The defender said: "It's very important to be in the top half of the table because the top six is always more exciting. So I hope we can finish in the top six this year.
"Everyone is focused and I think we can be in the top six.
"We had a good game against Inverness last week and the confidence is high now.
"Hopefully we can win this game. Motherwell are a good team, with good strikers, but hopefully it will be a good game for us."