Spalletti demands Italy learn from England defeat at Wembley
Gianluca Scamacca finished off a well-worked move to give the Azzurri the lead on Tuesday but Harry Kane scored either side of a Marcus Rashford goal as England came from behind.
The victory guarantees top spot in Group C for England, leaving Italy, the defending European champions, and Ukraine to battle it out for second place.
Spalletti's men are in third spot, three points behind Ukraine with a game in hand.
Whatever happens, they are already assured of at least a play-off spot due to their UEFA Nations League ranking.
Spalletti said his side had switched off at key moments.
"We were a bit casual at times but I do think we created a great deal, I think we were organised and I think ultimately we did create the conditions to do certain things well and that's besides the goal we scored," he said.
"But ultimately we weren't able to maximise those opportunities."
He added: "I don't think the lads necessarily deserved to lose by two goals this evening but we need to grow and develop as a team, particularly when it comes to those big match-winning moments and this is what European football is all about. It asks you serious questions."
Spalletti accepted that standards in Serie A were lagging behind those in other top European leagues.
"I think that's the case," he said. "Matches such as these ultimately need to motivate us and inspire us.
"We need to try and make sure we take something from this that allows us to ultimately withstand these physical confrontations, the pace and tempo of these matches.
"We have to develop when it comes to games such as these at European level but that's what we were trying to do tonight."
He said he did not fear anxiety from his players as they battle to qualify for the finals.
"I'm not afraid of anything and I'd be very surprised if my players showed any fear," he said. "I think we have the quality to play against any opposition."