The Rams were losing at half time, but they stormed back to record their fifth consecutive win, with Chris Martin netting a hat-trick.
McClaren told Sky Sports News: "Blackpool scored from a set-play freak goal and I felt we didn't start very well, but we grew into the game and in the last 20 minutes we played well and created a lot of chances.
"Basically, we ground Blackpool down, forced them into errors and into mistakes and we were fantastic."
The Tangerines also conceded two penalties, the first of which was awarded for a foul on Martin by Jack Robinson, although the offence appeared to take place outside of the 18-yard box.
McClaren admitted that referee Andy Haines's decision to award the first spot kick was harsh on Blackpool
After watching a replay of the incident, he added: "If I was [Blackpool manager] Paul Ince I'd be enraged about that one, but I'm delighted."
Derby are now fourth in the Championship table, with 34 points from 19 games.