The England stopper admits he perhaps should not have challenged Peter Crouch for the ball in the game with Stoke last weekend.
Foster damaged knee ligaments in a recent tie against Stoke and after assessment has been ruled out until October. He landed awkwardly in a challenge with Peter Crouch and told the official West Brom website that he regrets going to try and beat the giant striker in the air.
He stated: "I had a collision with Peter Crouch and even now I'm thinking 'what on earth are doing challenging Peter Crouch?' It was stupid on my part.
"As I landed I did so on a straight leg, which is always a no no because you want some bend in the leg to cushion in.
"You can see from replays that my knee buckled and I just heard this pop as I landed. I couldn't feel my leg or my knee and it kept giving way. It shut off completely. I hoped I had only jarred it but it became pretty obvious it was worse than that."
He was replaced by Boaz Myhill in the game against Stoke and he was originally ruled out for a month.
Instead he will miss the next six months as the knee damage he suffered has been confirmed as more severe than originally thought.
The club confirmed on their official website last weekend that he not only damaged knee cartilage, but also knee ligaments and he is out until October.
The problem is nothing new, which will certainly worry the stopper considering his age. He suffered cruciate knee ligament damage back in 2007 whilst with Manchester United and missed almost a year of action.
Foster and West Brom fans will hope he makes a swift but full recovery from his latest setback.