With signs of fatigue showing following Thursday's Europa League clash against Kuban Krasnodar, McCall put Henri Anier, Stuart Carswell and Zaine Francis-Angol on midway through the second half.
And the 49-year-old praised the trio's display, particularly Anier who made his league debut with the match-winning goal seven minutes from time.
"I'm delighted. I thought they started better but then I thought we controlled large parts without being dangerous," said McCall.
"And I thought in the second half the game on Thursday caught up with some of the lads, I thought we looked leg weary at times and I think the three substitutes helped gives us a bit of freshness.
"When you make substitutions you want your substitutes to come on and have an impact, and obviously Henri did that.
"So I'm really pleased with the victory, naturally, and a good start for the campaign."