Foster flapped at a cross and badly miscued a clearance that allowed Grant Holt to score into an empty net.
Ruddy, 26, said: "I felt sorry for Ben. I do not think the pitch was great and was holding up quite a bit once the water had dried out.
"Ben got himself into a position where he got mixed up with the defender but he showed his quality with a fantastic save from Pilks. He is a top quality goalkeeper."