"At half time I still didn't think we were home and dry because we had only played 45 minutes," The Black Cats boss said after the 3-2 defeat.
"Their first goal caused us a lot of pressure. It's too simplistic to say it's down to luck. West Ham may be euphoric but they were battered for 45 minutes.
"We're morose but we played well, scored twice and made lots of chances. We shouldn't have lost. With a bit more experience and calm we would have won."