Yeah, just looking at the player stat lines, one has to take into it that Kozak is 4.5 years younger than Murray. At the same age, Murray was playing for Youngstown of the USHL and had to come to the next camp to earn an AHL contract, let alone an NHL deal. Murray's playing PP time for Rochester - sometimes first, sometimes second depending on available personnel - and Kozak almost without fail does not and that lead to 8 goals and 13 PP points for Murray.
In just playoff terms, Jobst with Mersch and Murray on the wings had some matchup issues trying to slow down Barre-Boulet and were on for the last two Crunch goals in Game 5. I wouldn't look too deeply into the +/- thing. The Game 3 win was due in large part for what Murray did offensively an dhe still wound up -1.
They don't have Biro so they're playing Jobst up as C1 and Malone as C2 while Kozak was on Malone's wing much in Game's 4 and 5 with Rosen on the other side. He's been the sort of warrior mentality that Sabre fans will love when it translates up to the big club. He takes hits to make plays - the one were he gets crushed to feed Weissbach in Game 1 was something lesser players wouldn't have tried, they would've daisy curled and peeled off instead of eating the hit. If there is question of where an energy line replacement or two are coming from within the Sabres prospect cadre, Kozak is at the top of a very short list with Cederqvist for those sort of roles.