Manchester United forward Marcus Rashford risks burning out by the age of 30, according to former England boss Sam Allardyce.

The 21-year-old has already become an important player for United and England and his talent is expected to continue growing.

But Allardyce has warned Rashford to manage his workload in order to prolong his career.

"Probably very difficult to get to 30," the ex-England and Everton boss told talkSPORT.

"Because of the demands, physically and mentally, the fatigue that he will suffer. He will have three weeks a year off. That's it.

"He'll play all over the world because there's no pre-season anymore, they go straight away across to these tournaments.

"He'll play for his country in the summer and he'll get barely three weeks off.

"I think when you look at the wear and tear… by 25, he will have niggles. Even if he doesn't get any major injuries, the knees and the ankles, the hips, the back will be a little bit of a problem as he goes on.

"They won't stop him playing but I think later on in life it will bring his career to an end quicker than before.

"But if you look at the Premier League now, I think there's less players over 30 playing now than ever."