Frank Lampard admits it is no coincidence Chelsea's disappointing form has coincided with Hakim Ziyech's absence, with the winger potentially returning to face Manchester City. 

Ziyech has missed Chelsea's last six matches in all competitions due to a hamstring injury sustained in the 3-1 victory over Leeds United on December 5. 

That win lifted Chelsea to the top of the Premier League but they have won only one of their five top-flight games since, leaving them six points adrift of leaders Liverpool having also played a game more than the reigning champions. 

The Blues have a 27 per cent win rate in the 11 Premier League games Ziyech has not started this term, compared to 80 per cent in the five games he has featured from the beginning. 

And after seeing his wide players again fail to fully click in Monday's 1-1 draw with Aston Villa, head coach Lampard is eager to get Ziyech back involved again as soon as possible. 

"I don't think it's a coincidence," he said at his post-match news conference. "I can't rely completely on him.

"I think with Hakim, the way he was playing, he was being very effective for us in terms of assists, goal creation, chance creation and some goals.  

"He also had a real confidence in the way he was playing and we were very fluid at the time. He got injured when we were in a great run of form, so I think it has been a point.  

"You are going to miss players at that level when they drop out and we want him back." 

Chelsea have a six-day break before hosting Manchester City - a game that is now in jeopardy following a coronavirus outbreak at City, forcing the postponement of their trip to Everton on Monday. 

"There's a possibility Ziyech could be fit for that one if it goes ahead on Sunday," Lampard said. "I will know later in the week, but he is progressing to the point where he is close." 

Despite only featuring seven times in the Premier League since joining in the close season, Ziyech's total of three assists is bettered only by Timo Werner and Ben Chilwell (both four). 

No Chelsea player can match the Morocco international's average of 2.77 chances created per 90 minutes either, Callum Hudson-Odoi the next best for the Blues at 2.66.

Hudson-Odoi was recalled to the starting line-up for the visit of in-form Villa and, despite only managing a single shot, Lampard was pleased with the winger's overall display. 

"I liked his performance today and I liked the range of his passing, which was very evident in the first half," Lampard said.  

"He played a couple of great cross-field balls and some of his footwork, touches and movement were great.  

"The next part is the end product because we want to see Callum as he did against Arsenal, to go one against one, to be confident to go one against one, because he has the ability to do it. 

"The top wingers produce it in the Premier League in recent years and Callum definitely has capabilities. That will be the next stage for him."