England fast bowling consultant Allan Donald believes Andrew Flintoff's bowling action will need to be modified to avoid future injury problems.
Flintoff took 1-24 in Lancashire's Twenty20 Cup semi-final defeat
Flintoff has just resumed playing after a third operation on his left ankle and is set to be named in England's one-day and ICC World Twenty20 squads.
Donald says the way the all-rounder's front foot points inwards and twists on delivery is a concern.
"It's is a major issue that could creep up again," said Donald.
The former South Africa Test star watched Flintoff playing for Lancashire in their Twenty20 Cup semi-final defeat to Gloucestershire on Saturday.
That was only the second time that the 29-year-old Flintoff has bowled since his return after a three-month absence.
And Donald also revealed that Flintoff, who has not played for England since the World Cup, had spoken to him about his own concerns during England's Test win over West Indies in June.
It is not something I am going to start modifying now. It would have to be done in the close season
"I went to the ground specifically to have a look at Freddie. I sat on the scaffolding with my binoculars to watch him bowling," he said.
"At the moment Freddie is bursting at his seams, happy just to be out there playing and bowling again.
"The selectors and coach Peter Moores are delighted to have him back bowling, and he will make a massive difference in the one-dayers.
"Freddie talked to me during the Old Trafford Test when he was still on crutches and he asked whether we needed to work on getting his front foot straight.
"It is not something I am going to start modifying now. It would have to be done in the close season. It is up to Freddie to decide."
Donald's contract with England runs until the end of the ICC World Twenty20 in South Africa in September.