Di Francesco slammed his players' "attitude" after the loss.
He barked: "Sometimes freshness makes the difference, it is not the fault of young or old. Some players, see (Radja) Nainggolan, have always played. Today he did not make the best of it but he also had a blow and lost a tooth.
"I put him behind the striker to give him the opportunity to express himself, but it is not a matter of systems, but of attitudes."
Di Francesco continued: "We also managed something that did not make sense in the Champions League (against Shakhtar Donetsk).
"I struggle to give concrete answers, I have to confront myself and do something more."