Ward saluted Lee's superb save to deny striker Eliot Richards and claimed his players had the chance to take control of the game in the first half.
Jay O'Shea and Armand Gnanduillet secured the points for Chesterfield in the second period.
"It was a great save," he said. "It was a great shot and an even better save because it looked a goal. Fair play to Tommy, he's an agile and capable goalkeeper and that's what he does.
"That's got to be right up there with his best because everyone in the ground thought it was in.
"But I think we missed an opportunity in the first half. I think Chesterfield had their first effort after 31 minutes and we had a chance if we could have raised our game in that period.
"But once they got their goal they looked a very good side, their tails were up, their confidence was restored and we found it very difficult to compete with them in the second half.
"I have no complaints about the result and the better team won but we missed an opportunity."