O’Brien played alongside this season’s Championship top scorer Zan Vipotnik during his spell with the Swans last season.
The Slovenia international has netted 17 league goals so far this term, and O’Brien admits Wrexham’s backline will have their hands full when it comes to keeping an eye on the striker.
“He’s having a great season, he’s always had the quality to be able to do that,” O’Brien said.
“There’s a lot of strikers in the league at the moment that are firing all cylinders and he’ll be a hard one to keep quiet.”
Swansea’s 2-1 victory over Portsmouth at Fratton Park on Tuesday moved Vitor Matos’ men to within five points of the Red Dragons before the meeting between the sides on Friday.
But only Millwall have averaged more points per game than Wrexham in the Championship since the Swans beat Wrexham 2-1 in the reverse fixture on 19 December.
And while excitement among fans has grown before the second contest of the season between the sides, O’Brien remains determined to treat the fixture like any other.
“People can big up this game as much as they can, but I think we just have to see it as another game,” he said.
“We can’t have the occasion get too much for us or us think that it’s a bigger occasion than it actually is.
“It’s another game in the Championship – that’s how we’ve got to see it.
“It’s a Friday night under lights, it’s the Welsh derby and everything, but at the end of the day, it’s two 11s going against each other like it is every week.”
