An own-goal from Mat Sadler before half-time and a header from Franck Moussa gave the Sky Blues a two-goal lead, before late strikes from substitute Jamie Proctor and Andy Drury secured a deserved point for the Reds.
Whittingham was delighted that substitutes Proctor and Sergio Torres, whose cross was diverted in by Drury for the second, made a huge impact on the game at Sixfields.
"Credit where credit's due to the lads who came on," said Whittingham.
"One's scored for us and the other one made a run for the second. You need that when you come to places like this, you need players on the bench who can come one and make an impact.
"Coming here and getting a draw is a good result.
"In the second half we came out and really took the game to them, we were deservedly back in the game. When you come to Coventry they're a good side, it takes a bit of getting used to how they move the ball around.
"We've certainly got the heart. The positives outnumber the negatives. The biggest thing we've noticed since we've come here is the camaraderie of the team and the team spirit and the desire, they've shown it at Preston and they showed it here, in another really encouraging performance."