The Blues scored three late goals to give the scoreline a comfortable look, but Di Matteo believes that their first-half performance was "slow".
However, the 42-year-old was happy with his side's second-half showing, as well as the fact that they kept a clean sheet while securing all three points.
"I think we were a little bit slow in the first half, and much better in the second half. The goals came at the end and they took a bit of time," said Di Matteo.
"All in all I think it's a good scoreline for us, three points, a clean sheet away from home as well, so it was a pleasing night."
Chelsea's next match comes at home to Norwich City in the Premier League on Saturday.