He has nothing but sympathy for injury-plagued Hargreaves, who Foster also saw at his best at Old Trafford.
Foster told the WBA website: "If we can sign Owen Hargreaves, and he would stay fit and play every Premier League game next season, then you've got a £15million player on your hands for nothing.
"It's as simple as that. He's an amazing player. He's got so much ability. What's happened to him over the last few years has been such a cruel thing to happen.
"I did my cruciate the same time he picked up his first injury. I spent a lot of time with him in rehab and getting back to fitness. He never really seemed to find answers to what was wrong with his knee.
"I've heard he's in pretty good nick at the moment and he's looking to find a club. If you can get a fit Owen Hargreaves he's a valuable, valuable asset to you.
"In the one full season he had at United he was amazing. Off the back of that he was one of England's shining lights at the World Cup.
"He's a great player, and not only that, he's a great lad around the place as well.
"He's happy and cheerful - a good egg to have about."