McCusker's men fell to a 36-17 defeat to the hands of Sale Sharks in their last outing, despite being 14-3 ahead following an impressive start.
Leicester are flying high in the Aviva Premiership, currently sitting third just three points behind defending champions Harlequins and are unbeaten in nine.
And 27-year-old skipper McCusker, who has five Welsh caps to his name, believes his side must improve quickly on their Sale showing if they are to beat the Tigers.
"Ultimately the result wasn't the best, although we did get some positives out of it," he said. "It wasn't an ideal result by any means, but Sale were pretty much at full strength.
"It's hard as morale and confidence is a bit low after some quite weak performances, and we need to get the boys going again.
"We had worked on a few things like shortening things and emphasising the first few phases to get us going forward.
"We had a good start in that game, and although our tries came from a couple of errors we were putting a lot of pressure on them.
"It was pleasing to get a few tries against them, but their try on the stroke of half time swung the momentum in their favour and it was an uphill battle from there.
"Sale kept the ball a lot better - we didn't really have any field position and against a quality team like them you are always going to struggle."
Despite being well placed in the league the Scarlets are without a win in five, while Leicester are bang in form in the Aviva Premiership, having lost just three league games this season.
And McCusker insisted the Parc y Scarlets side must change the atmosphere in the changing room as they search a return to their early season form.
"Playing Leicester will be very tough - they have obviously lost a few boys to the Six Nations, as have we, but they still have a pretty strong squad," added McCusker.
"It will be a real test for us whoever they bring, but we need to grab the game by the scruff of the neck and get a home win."
