"Sometimes I think why did we let him go, to be honest with you," the Daily Mail quotes 30-year-old Foster as saying. "It's not even hindsight.
"He was one of our best players from the last couple of years and it's disappointing that he's no longer here. When he went, it was obviously a big blow for us because we know what Shane does.
"He will give you 110% every single minute of every game. He's a fantastic player and we would love to have him now."
West Brom are currently 16th in the league table, three points above the relegation zone.