The fight for the top four position has become very tight because some teams have improved after the sack of coaches. Roma and Napoli fall in this category, since after the sack of Jose Mourinho and Walter Mazzarri. Francesco Calzona and Daniele De Rossi are gradually changing the fortunes of these teams. I just hope they maintain this good performance.
For Roma I think they can do it but for Napoli they won't be able to do it until the end of the season. Napoli still have to improve their overall performance and even though they have just won against Juventus, this cannot be a strong guarantee for them to continue to progress with consistent wins.
I wouldn't be too sure about the assumption that Napoli is out of business for the top four. Roma has been playing great lately and it looks like the change of the coach had some effect. Actually, I admit that I thought it might have a short-term effect and then Roma would start losing games again that they should actually win. But no, apart from the game they lost against Inter Milan, which is totally understandable, they have been performing way better than anyone expected after they sacked not any coach, but Mourinho himself.
Now for Napoli the job is a good bit harder I admit. But I think that they are still in distance to strike back and to make up for some points if they can win some games in a row. So nothing is over yet for them and by the way they are still in the Champions League. The first game didn't look all too promising, but let's see.