Toro won 2-1, with Vanja Milinkovic-Savic producing a series of wonderful saves in goal.
“It's a pity, because we created a great and got the defending wrong on their set plays, but considering what the team created and the way we dominated the game, it was a positive performance," Di Francesco told Rai Sport.
“It was also our own fault that we didn't finish our chances and we must be more determined in front of goal."
This was the third consecutive penalty not converted by Edin Dzeko, who had only just come off the bench.
“As he wasn't in the starting XI, he was not the designated penalty taker today, but when a player feels he's up for it and confident of scoring, it's right that he should take it. Unfortunately, this could now weigh on him psychologically."