"The sending-off was a clear one, but of course it changed the game," Delia told BBC Sport.
"We created a lot of chances today. We could have created more in the second half, but we have played a lot of matches now and we have two important matches coming up next week.
"The boys are working hard, they all want to perform and get better, and today was a good start."
Celtic face Partick Thistle in the Scottish League Cup on Wednesday, before welcoming Inverness Caledonian Thistle to Celtic Park next weekend.