Ward, 21, was substituted in three out of four matches prior to Saturday's last-day win and started on the bench in the other, but capped an impressive display with his fifth goal of the season as he played the full 90 minutes against Yeovil.
"Danny Ward was very good and took his goal well," Grayson told the club's official website. "I have always rated Danny very highly and you can keep telling players how good they are, but they have to believe in themselves.
"He has got undoubted talent and you could see after he got his goal that his confidence grew and he almost got another. There's a lot more to come from Danny."
Grayson rested leading goalscorer Jordan Rhodes again ahead of Saturday's first-leg play-off semi-final at MK Dons and was with replacement Kallum Higginbotham alongside Lee Novak.
"It's possible that I could pick all three and accommodate them into a system," Grayson added. "Whatever team I pick will be for the sake of the football club and not the individual."