While Napoli are still 15 points ahead of second-placed Inter Milan, another loss could reignite their rivals' fading hopes of catching up with 13 rounds left in the season but Spalletti said his team remained focused.
"From what I saw of the attitude and the disappointment when we got back into the locker room, it was a game that went a bit wrong, but nobody here has taken their hands off the wheel," Spalletti said.
Sixth-placed Atalanta are five points off fourth, the last Champions League qualifying spot, but have not won any of their last three league games and failed to score in their last two.
Napoli will be without the suspended Mario Rui, while Gian Piero Gasperini's Atalanta side will not be able to call on key players Teun Koopmeiners and Davide Zappacosta, who are injured.
The race for the top four
Meanwhile, Simone Inzaghi's second-placed Inter travel to Spezia on Friday having dropped just five points in their last six games as they look to cement their place in the top four.
While qualifying for next season's Champions League is a priority for Inzaghi, he will also be focused on the second leg of their last-16 tie at Porto on Tuesday where they will be defending a 1-0 lead.
"Obviously, we could've done more in the league, but we've also done some great things over the past 18 months," Inzaghi said.
"We still have more matches to play this season and we must play the way we did (in last week's 2-0 win over Lecce)."
Juventus hit a speed bump last week in a 1-0 defeat by Roma - their first loss since January - but they have made up ground since their 15-point deduction to move up to seventh.
Juve host a struggling Sampdoria side who sit rock bottom - nine points from the safety zone - and at risk of ending their 11-year streak in the top flight.
Defending champions AC Milan will host Salernitana on Monday, as they look to get back in the top four. Stefano Pioli's side are fifth after a 2-1 loss against Fiorentina last week.
Milan received a boost after knocking Tottenham Hotspur out of the Champions League on Wednesday to reach the quarter-finals for the first time since 2012.
Third-placed Lazio's impressive victory over Napoli was bittersweet as they lost Ciro Immobile to a muscle injury, with the striker set to miss Saturday's trip to Bologna.
"Since last year, when he hurt his ankle, he's never been well... He played with pain-killers for the ankle problem, which I think is causing him discomfort," manager Maurizio Sarri said.
Jose Mourinho's fourth-placed Roma will face Sassuolo at home on Sunday. The visitors are on a good run having won four of their last six league games, losing only against Napoli.
