"It was disappointing. We found it difficult here last season and this season again," said Di Matteo. "We knew West Brom are very good at home and giving away goals like we did today it became difficult to win a game.
"Our defending was very poor, we didn't concede many chances but with the ones we did we have to do better.
"We had plenty of chances to score but you have to score them and you can't always rely on three goals to win a game. You have to make sure you are focusing on your defending and are responsible to bring the points home."
Chelsea host Manchester City at Stamford Bridge next Sunday.