McGrath is in the final year of his contract at the Buddies which means he can sign a pre-contract agreement with clubs from January.
Goodwin is aware that there is every likelihood St Mirren will lose the midfielder midway through the season or next summer.
“I wasn’t anticipating losing him, but as usual the carry on starts on deadline day and then there was serious interest in him,” he told the Scottish Sun.
“I’m delighted he’s still here. Jamie would be well within his rights if he signed a pre-contract with another club in January.
“Equally, if someone comes in with an outrageous bid for him we’d need to decide what’s best for all concerned.
“Right now, we don’t need to worry too much about that.
“Ideally we’d like to tie him down on a long-term contract, but realistically, that’s not going to happen.”
McGrath has shot to prominence since joining from Dundalk in January 2020.
Under Goodwin, he has been moulded into an all-action midfield and he earned his first cap for the Republic of Ireland last week, putting in a starring display, including an assist, in a 2-1 loss to Portugal.
“I saw that potential for growth prior to signing him,” Goodwin said.
“He had been pigeonholed as a No .10 at Dundalk and people looked at him as a luxury player, but I had a very good conversation with Jamie and his representatives and explained that I saw there was more to him than that.
“My belief was that he could become a No .8 and be a box-to-box player and I think he’s shown he can do that.
“He’s not one to fly into tackles, but he gets close to opponents, he’s fit, he’s quick and his composure on the ball is incredible.
“His creativity and bravery when in possession is second to none.”
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