Specialists will assess the results of a scan on Michael's groin on Monday evening, and, if he requires an injection, he will miss the European Championships in Switzerland.
"I'm still not sure what is happening because my groin is sore again and I have to see a specialist," he says. "It means the season could finish a bit bad for me, after a good last day all round.
"Hearing the news was a bit disappointing because I thought I had the problem out of the way, but it has been a bit sore now for the last couple of weeks.
"It would be nice to go away and represent my country after a long season, but it is about me - I have to get myself right.
"I don't want it dragging on to next season, and I have to be ready for the start of the new campaign - West Ham is definitely the priority."
Michael may yet be cheering on three West Ham team mates in the World Cup with Trevor Sinclair now on standby because of injuries to Keiron Dyer and Steve Gerrard.
"I was delighted for Joey getting picked. Jamo was more of a cert but in the last couple of games Joey has done really well," says Michael.
"All the boys are delighted for him, but Trevor was really unlucky not to be in the original 23 because I thought he had done enough to get there.
"It was a case of congratulations to Joey and Jamo but commiserations to Trevor, but he will bounce back, perhaps sooner than we think!
"He showed on Saturday he was strong enough to bounce back and that it hadn't affected him too much."
Michael's disappointment at not making the full squad himself, and now possibly missing the under-21s as well, has been assuaged to some degree by his satisfaction at finishing seventh in the Premiership.
"It was brilliant, especially for the gaffer, who has come through some hard times," he says. "It was his first big job, and to do what he has is magnificent."
Michael was indignant about the criticism Glenn Roeder received at the start of the campaign, and says: "It was down to the lads not performing, not him, and fair play to the boys to finish seventh after being in the bottom three for the first couple of months.
"It is something to build on for next season."