The forward returned to the side after nursing an ankle picked up in a win at Bologna.
Things have not been plain sailing for Juventus in recent months.
The arrival of Cristiano Ronaldo was supposed to be key in helping them win the Champions League but those hopes are now in serious jeopardy.
Juventus will need to overturn a 2-0 deficit against Atletico Madrid in Turin in nine days time if they want to win European football’s ultimate prize.
The result at the Wanda Metropolitano and defeat in the Coppa Italia at Atalanta will have left Ronaldo and his team-mates frustrated.
A bizarre incident before the game suggests the Portuguese star is a little tense at the moment.
A camera inside the dressing room got up close and personal with Ronaldo as he put on his socks before the clash with Napoli.
Ronaldo did not like being interrupted during his pre-match ritual and he ushered the camera away.
One fan on Twitter seemed to agree with Ronaldo’s action, claiming the frame was a bit close.
They tweeted: “A panned shot of the dressing room showing players getting ready is OK.
“Specifically moving in and focusing on one while he’s dressing is invasive. I agree with his reaction.”
Another put: “I understand, would be so annoying.”
Ronaldo did not seem to be enjoying himself much on the field either, at one point in the match he was seen shaking his head at the bench.
He was knocked over by Napoli goalkeeper Alex Meret, who was shown a red card.
Miralem Pjanic took the resulting free-kick and scored past former Arsenal goalkeeper David Ospina.
Emre Can doubled the lead for Juventus before Jose Callejon pulled a goal back in the second half.
Lorenzo Insigne then missed a late penalty, the win puts Juventus 16 points clear at the top of Serie A.