Allan, who was part of a failed summer swap deal that would have saw McGrath head in the opposite direction to Easter Road, is out of contract at the end of the season.
It appears the former Celtic playmaker is unlikely to feature significantly in new manager Shaun Maloney plans at the capital club.
The 30-year-old is also believed to be interesting Dundee, where he spent time on loan during the 2017/18 season.
The Buddies boss revealed McGrath had asked to be left out of his squad ahead of their Premiership clash with Dundee United at Tannadice last night.
The Republic of Ireland international, who turned down a move to Aberdeen earlier this week, has been the subject of increased transfer speculation in recent days.
Goodwin admitted: “There’s been a lot of speculation. Jamie did not feel his head was in the right place for the game.”
Saints are thought to be holding out for £350,000 for the former Dundalk midfielder and until McGrath’s future is cleared up, it is understood the Renfrewshire outfit don’t have the resources to bring new players into the club.
Should their valuation be met in January, Goodwin is likely to swoop for Allan, who has featured predominantly from the bench so far this season, making 18 appearances.
No contact has yet been made with Allan but Goodwin has already spoken of his admiration for the player.
Speaking to Renfrewshire Live Sport, he said: “Scott Allan is a player I’ve always admired.
“He’s got really good technical ability, a very creative type, but we’ve got a number of players like that at the moment in the squad.
“Before we bring anyone else into the group realistically we’re going to have to let one or two go first.
“There’s not a endless pot of money here in Paisley. We’ve got to balance the books like the majority of the clubs out there.
“That’s the situation we’re in, but Scott is obviously a player that was linked with us in the summer as well.
“If everything had transpired the way we thought it would then Scott would probably be here, but at this moment in time we’re not speaking to Scott or his representatives.”