Napoli coach Maurizio Sarri defended his team selection after defeat at Champions League opponents Shakhtar Donetsk.

Dries Mertens came off the bench to earn a penalty, converted by Arkadiusz Milik, but the Partenopei lost their Champions League opener 2-1 in Ukraine.

Sarri was asked why top scorer Mertens was left on the bench in favour of Milik.

“Yesterday I was accused of not making enough changes, now I am accused of too many. Dries is extraordinary and we don't leave him out lightly, but pace is his greatest strength and he can't have 50-55 games per year. He was coming off international duty too, so we decided to rest him and let him come on later.

“If we had managed to keep it on 0-1, he could've got us the equaliser. He has certain characteristics and qualities, so it's not easy to leave him out, but sometimes we have to.

“Shakhtar have very physical defenders, but their forwards are fairly lightweight and focused on quality. The choice of Milik was a general one. Mertens has recovery rates that are different to Lorenzo Insigne, those are what our statistics tell us, so he needs rest."

On Marek Hamsik lasting just an hour, Sarri continued:

“Marek is going through a period where he's not very sharp, but that happens to every player at one stage or another. I thought he did better tonight than in other games.

“You always need to give something for your teammates and right now Marek needs help from his teammates. He needs a while every season to get into form and in order to reach form he has to play regularly, so in my view it's right to keep faith with Marek."