The 25-year-old asked to be left out of the trip to Dundee United last week and also sat out Saturday's Scottish Cup fourth-round tie at Ayr.
Ahead of the cinch Premiership game against Aberdeen on Tuesday night, Goodwin hinted McGrath could be ready to return to the squad.
"James is still very much a St Mirren player and still very much part of my plans. There's a lot of speculation floating about, but until something is confirmed, or otherwise, he will remain part of my squad, " said the Saints boss.
"He's in a good place now and he trained really well this morning. All the noise about whether he is or isn't moving was affecting him and we have had a chat and I have asked him to try to put all that to the back of his mind.
"It can be distracting when there is speculation flying around, I've been there myself, but we have had a really good chat this morning and he just wants to get back playing football.
"James' priority now is to play games for St Mirren and keep himself in the mind of (Republic of Ireland manager) Stephen Kenny, because James is no good to anybody if he is missing games for us.
"Agents are there to deal with all the off-field stuff and he just needs to get back to doing what he is good at – playing football."
Asked if he thought McGrath would still be at the club when the transfer window closes next week, Goodwin replied: "It's very hard to say to be honest with you.
"I didn't expect him to still be here after the summer window, but here he is. He needs to get back playing for St Mirren and what will be will be thereafter.
"But what can't happen is all this impacting his game or mentality. If he signs a pre-contract with someone then so be it, or if he leaves this month and we get a fee then so be it."
St Mirren have won both matches that McGrath has sat out. The victory at Dundee United was Saints' first since mid-October and Goodwin's side followed that up with a cup success at Ayr.
Captain Joe Shaughnessy said: "It hasn't been a distraction at all and the lads that have come in have done really well.
"Greg (Kiltie) has a couple of assists and scored at the weekend. There's plenty of quality in the squad to go and win games and there's confidence in the team and squad.
"Jamie is a lovely lad and he trains away and we have all just been getting on with it. I'm sure it will sort itself out.
"As captain, I've had no need to get involved as Jamie has been training hard every day, and besides it is none of our business."