Ziyech has endured an underwhelming first season in the Premier League following his £33.3million move from Dutch outfit Ajax last summer.
The Morocco international has scored just once in 15 Premier League appearances and was subbed off by Blues boss Thomas Tuchel during Saturday’s goalless draw with Leeds United.
Asked why Ziyech is struggling in west London, Melchiot told Stadium Astro: ‘He doesn’t always get the opportunity. I think Frank [Lampard] understood him better, he wanted him and went after him.
‘I think Ziyech is facing now what he had at the beginning at Ajax. It was kind of difficult for him to get a run going. Once he got it, he was among the top-two players in the team.
‘Now in the Premier League you have many stars around you. He has to understand that.
‘I think it comes down to rhythm. If you don’t play that often, when you get your opportunity you have got to grab it.
‘But it can take a few games to get up to speed, so if he doesn’t get those games, it becomes really tough.
‘I like him and I think he’s technically gifted, physically fit and understands the game well.
‘At Ajax he would cross the ball so many times and there were players on the end of it. They need to understand [at Chelsea] what his strengths are because if he can deliver that and really master that, it could be something special, if not then it becomes tough.
‘I know he won’t like it, he’s not a player who’s used to coming off the bench. He was a starting player every time at Ajax.’
Tuchel, meanwhile, admitted his Chelsea team needed to be ‘more clinical’ after they were held to a 0-0 draw at Elland Road by Leeds.
‘We have enough quality to use the chances better and to be more clinical,’ said Tuchel. ‘It is our responsibility, my responsibility to create more and to maybe have more big chances.’