The head coach is taking time out after having emergency hysterectomy surgery in her ongoing battle with endometriosis two weeks ago.
Ahead of Aston Villa's trip to face the Women’s Super League champions, general manager Paul Green offered further insight into Hayes's recovery.
“Emma is making good progress,” Green said. “It's still too early to put a timeline on it.
“We are speaking to her every day. She was delighted with the performance the other night. She had a comfortable night’s viewing and a great performance.
“But yes, she is getting better. I don’t think it will be too much longer but, as I say, I don’t want to put a timeline on it.”
Meanwhile, Chelsea have handled her absence well, winning all four games through the joint leadership of Green and assistant head coach Denise Reddy.
Green added: “I think she is happy with the way the team is going and the work Denise, I and the coaches are doing. We have won every game so far so we have to try to maintain the team in a good position whenever Emma comes back.
"We’re enjoying it but will be delighted when Emma is back."
The pair have had regular contact with Hayes who continues to watch every match and training session from afar.
She will have seen Fran Kirby return from the bench in the 8-0 win over Vllaznia Femra in the Champions League in midweek.
“Fran is back in training, you saw she came off the bench in midweek,” Green added. “She is fully fit we just need to be careful with keeping her fit and reintegrating her into the team. She will be in the squad on Sunday and we will see how much involvement she gets.
“Certainly, we are delighted she is back in the squad. It gives everyone a boost. It’s just with her injury and illness history that we need to carefully manage her in the right way.”
They do, however, have several fitness concerns after playing three games in seven days.
“Jelena Cankovic is still ruled out. Her injured hasn’t settled down as quickly as we had hoped,” he noted.
“Maren Mjelde is still out, she has taken a little bit longer to recover from the PSG game so she is a precaution. Melanie Leupolz is still unavailable whilst she is on maternity leave.”