Collison, whose father died in a motorcycle accident last month, was intent on playing in both Wales matches over the next few days.

He will be given compassionate leave from the Wales camp to attend his father's funeral on Monday.

The 20-year-old had insisted that he wanted to play for the Wales under-21s against Italy in Swansea on Friday as well as for John Toshack's senior side against Russia in a World Cup Group Four qualifier in Cardiff next Wednesday.

But Collison "tweaked" a calf muscle in training on Thursday and is now doubtful for the Liberty Stadium match, a UEFA Under-21 Championship qualifier.

Under-21 boss Brian Flynn said: "Jack has been fantastic in training this week, considering the pressure he is under and the emotions surrounding his dad's death.

"But he wanted to play in both matches and we were happy for him to do that. Then he manages to pick up a calf injury in training and must be doubtful for the game against the Italians.

"We are mindful that if he plays in the under-21, he may damage his chances of playing against Russia next week."

Flynn has other injury and sickness worries. Striker Ched Evans is suffering from a stomach bug, Simon Church has an ankle problem and Cardiff's Adam Matthews - a late call-up - has picked up a muscle injury.

Flynn said: "This will be a very tough match, as difficult as when we played against England in the previous UEFA tournament last season. What we did not need was any more injury problems."

Flynn has already lost Nottingham Forest full-back Chris Gunter and Bristol City centre-back Lewin Nyatanga through injuries, although both will join up with the senior squad next week.

Flynn also has a major doubt over Swansea midfielder Joe Allen with a hamstring injury.

Collison's father Ian, 46, died in an accident on the M25 on August 23 when he was travelling to see his son play for the Hammers against Tottenham.

Watford-born Collison, who qualifies for Wales through his grandfather, did not know of his father's death that day until after his side's 2-1 defeat.

But he played against Millwall 48 hours later, and then at Blackburn on Saturday before joining joined up with Wales on Monday.

Collison will attend the funeral on Monday and then return to the Wales squad HQ near Cardiff the following day.

Toshack will rearrange his training schedule to accommodate Collison's wishes.

The seniors, who face a tough clash with the Russians, will now train on Tuesday afternoon rather than the morning.

Wales will make a late decision on Collison's fitness tomorrow, and still have some hope that he will join Arsenal youngster Aaron Ramsey in the side to face the Italians, as Flynn attempts to use his most experienced players against one of the best under-21 sides in Europe.

Wales are currently top of Group Three, and know that they must take points from Italy to qualify for the finals, having failed only in a play-off with England to reach this summer's finals.