The Bantams were beaten 3-2 at Valley Parade on Thursday night ahead of the return leg this weekend.
"This tie is very much alive but it won't be if we defend and play like we did in the first half, because we were very poor defensively, probably the poorest we've been all season, the basics of the game went," Parkinson told Sky Sports News.
"But in the second half we defended a lot better, showed good character because there's a lot of pressure in the playoffs.
"Now we go to Burton on Sunday and the expectation is on them and we're 1-0 down and we're right in this game."
Bradford travel to the Pirelli Stadium for the second leg on Sunday.