Scotland under-21 international McGinn, who is out of contract at the end of the season, now faces the prospect of missing the remainder of St Mirren’s bid to avoid relegation from the Scottish Premiership.
McGinn was left in shock and agony last Thursday when the prank at St Mirren’s Ralston training ground went horribly wrong, Thompson accidentally launching the pole into him after being tackled by his young team-mate.
The veteran striker has expressed his remorse and donated his win bonus from Saturday’s 4-1 defeat of Kilmarnock, in which he scored twice, to McGinn.
St Mirren have declined to make any official comment on the incident but will hold an internal inquiry. Manager Gary Teale is understood to have confronted Thompson at the time of the incident, although all parties have accepted it was a complete accident.
“I’ve obviously lost a player to an injury so I’m not making light of it at all,” said Teale. “I don’t think Thommo is making light of it either. He was really shocked that it happened as he never intended it.
“It was just a freak training-ground accident. I’ve never come across anything like that before in all my time in football and I wouldn’t expect to come across it again. Thommo has shown a lot of remorse from it. You can’t put it into the category of ‘it’s just one of these things that happens’ because it’s not. It was an accident. There was no anger, frustration, intent or anything like that. It was just something silly that went on.
“I spoke to Thommo about it at the time. He knew himself as soon as he did it that he was in the wrong. He’s shown a lot of remorse and hopefully we can soon put the incident to bed.
“John is going for a scan on Tuesday and he could be out for the rest of the season now. We hope not but we won’t know until we see the results. You don’t want to lose good players out of your side, certainly not because of incidents like this. We just hope he’s back as soon as possible.”
Thompson described the incident as the “worst thing I have seen in my life” as he recounted it in a newspaper interview.
“The whole thing has been a complete nightmare,” said the former Scotland international. “John is going to be okay but I’m mortified that it happened in the first place. I was having a carry-on and it turned sour. It was a stupid prank, something silly, and it ended with John being injured. I can’t apologise enough
“It’s all I’ve been able to think about since it happened on Thursday. I feel so bad. It was an accident but it’s still something I regret. We were doing a drill where, to score goals, we had to dribble between two poles which were sticking in the ground as gates. When I got to a set of poles John tackled me and one of the poles got stuck between my legs.
“It sounds stupid now but for banter I grabbed one of the poles and pretended I was doing some kind of Ninja move. I threw it into the ground behind John who, by this point, was running away and facing in the other direction. But as I did that, he did a Cruyff turn and the pole stabbed him in the leg. We were only a few feet apart. It wasn’t as if I launched it ten metres like a javelin. He was right next to me. I just hadn’t counted on him changing direction when he did.
“It was just horrendous. It was the worst thing I have seen in my life. It popped in and out of his thigh instantly and for a few seconds his leg was black. But then blood started pouring out of the hole.
“John was obviously in agony. A few of us carried him inside and he got treatment. I’ve been shocked by it and really down. I like a laugh and a joke in training but for this to happen is just unbelievable.”