It looked as if was going to be a bleak and embarrassing afternoon for the Tigers as they conceded four tries in the opening 13 minutes and trailed 28-0 after just 23 minutes. But a more determined and gritty second-half display restricted the home side to just one more try, and Castleford were rewarded with tries by Justin Carney, Michael Shenton, Richard Owen and Jake Webster.
Millward said: "We were up against a really talented squad who are worthy favourites for Super League and for us it was really foreign territory, with eight new faces, and to see where our young kids were. It was tough early on as we had only two completed sets in the first 15 minutes, so had no ball."
He continued: "I thought the opportunities that arose Warrington took them very well and we got some tough calls which I'm really keen to look at on the video.
"At half-time I was quite positive and in the second half our enthusiasm, toughness and desire was great, but on a couple of occasions our execution was just off when we looked a little bit rusty.
"I thought if we could have got one or two tries we could have made it a great last 10 minutes and really been pushing for the game. We blew a couple of chances but I'm really proud of the players, because they could have easily been derailed into losing sight and structure.
"But it was a good performance first up against a very talented team who make it tough for you."
Warrington coach Tony Smith was content with his side's first hit out of the season which brought the expected victory. Smith said: "We were probably a little bit scrappy with the ball at times but I thought our defence was was pretty good for a fair amount of the game.
"But we did some really good stuff as well today and, with the amount of penalties in the match and the amount of ball turned over, you are going to concede a few points. I thought Cas had a real dig considering the scoreline was so heavily against them early on, they never gave in.
"We did okay against a team with some attacking ability who ask a lot of questions of teams, and against maybe one of the lesser teams Cas might have had a good day. But it was a good work out for us and we have a bit to work on, but we expected that with it being our first game of the year."