Kozluk enjoyed a successful three-year stint with the Tykes before a move back to Bramall Lane in the summer.
"I`ve got a lot of good friends at Barnsley," said Kozluk.
"It will be difficult on Saturday as I want both clubs to do well.
"But I`m back with Sheffield United so I want us to win the match.
"So you have to put all those friendships behind you until after the game."
Source: PA
