Gresko is currently on loan at Rovers from Italian side Parma and he has impressed the Rovers boss enough for him to want to make the deal permanent.
"I think he's the answer," Souness told the Lancashire Evening Telegraph.
"He hasn't played a great deal of football this year and it can sometimes take half a dozen games for some people to get up to speed the way the Premier League is. But he's a naturally fit boy and a ridiculous trainer.
"He's a good defender and when he does get his full fitness, I think you'll see more of him going forward.
"So we'll see what happens, but we've all been impressed by him."