Chelsea boss Antonio Conte has ruled John Terry out of Saturday's Premier League clash with Arsenal at Emirates Stadium.
The veteran centre-back was forced to miss last Friday's 2-1 defeat to Liverpool after picking up an ankle injury in the 2-2 draw with Swansea City.
Terry returned to training this week, but Conte says he will not be ready for the game against Arsene Wenger's men.
"John didn't recover. He's working, but he didn't recover for the game against Arsenal," he said.
"I don't know [when he'll be back]. In this case, it depends on what the player feels."
Chelsea's strong start to the season has been undermined by defensive frailties in recent games, with Conte's side conceding twice in each of their last three fixtures in all competitions.
A 2-2 draw with Swansea City and a 2-1 home defeat to Liverpool have seen the 2014-15 champions slip five points behind early pacesetters Manchester City and a defeat to Arsenal will see the Gunners pull three points ahead in the table.
Conte, however, says defensive concerns are nothing new at Stamford Bridge and has called on the team as a whole to become more solid.
"When we concede a goal, all the team concedes a goal, not only the defenders," he said. "We must improve together to improve the defensive situation.
"This was already a problem last season - Chelsea conceded 55 goals. We must work a lot on this aspect."
On a more positive note, France international Kurt Zouma is close to making his return from a long-term knee injury, with Conte expecting the centre-back to return to team training within the coming days.
"I hope to see Zouma in full training in the next week," he said. "He is in good shape."