North End were a goal down to their lowly opponents when Grayson introduced striker Graham Cummins and defender Paul Connolly after the hour.
Cummins led the line impressively, while Connolly's introduction allowed Keith Keane to move into midfield and net the Lilywhites' equaliser with a fine strike 13 minutes from time.
"I was pleased that when we made the changes the players who came on or moved around the pitch had an impact on the game," Grayson told Preston's official website.
"Graham Cummins held the ball up well and Keith Keane gave us a base to play from and it was a magnificent goal, that was a bonus for us.
"If you ask Keith, he will say he's a midfield player who has adapted to playing right-back and his versatility is excellent for us. You need that flexibility so you can play different formations during games."
Forward Stuart Beavon (concussion) and midfielder John Welsh (Achilles) hope to return having missed out against Pompey, while Joel Byrom (hernia) and Scott Laird (broken leg) continue their respective recoveries.
- Sports & Recreation
- Keith Keane
- Graham Cummins
- Paul Connolly