A couple of earlier approaches were rejected by the Perth side, who were still involved in European competition at the time and enjoyed the possibility of stringing out that association until at least December, via the Conference League group stage.
But having fallen at the final play-off hurdle, losing out to Austrian side LASK on Thursday night, Hibs have re-opened talks with the McDiarmid Park outfit and submitted an enhanced offer.
Hibs boss Jack Ross has made no secret of his desire to bolster his defensive options, with McCart one of the names featuring high on his wishlist, and the club have made their latest move.
However, they are not the only ones looking to recruit the 24 year-old Scot. Swansea City and Bournemouth are both keen on the left-sided centre back, while Saints boss Callum Davidson, speaking after his team’s European exit said that he wanted to try to keep the squad together.
But, he admitted that it would be an interesting few days ahead of the transfer window closing on Tuesday.
“I’m obviously hoping we bring in more players than sell players but we’ll see what happens, it’s football,” said Davidson.
But he did insist that none of his stars, who won both domestic cup competitions last season, would be moving on unless “the price is right”.
Hibs have brought in new signings in midfield and up front, adding Daniel Mackay, Jake Doyle-Hayes and Hull City loanee James Scott, while making Jamie Murphy’s switch from Rangers permanent and agreeing a contract extension for Martin Boyle.
But they have limited cover at the back. That was exposed by Paul Hanlon’s recent head knock. Darren McGregor, 36, has been deputising for the captain but there is no real depth in that area and McCart is, undoubtedly, a preferred choice to help them address that.
But, with time running out and Ross admitting he would have liked to have new faces in the squad before now, the club are also chasing a couple of alternatives if their current offer is rejected and the McCart transfer does not pan out.