Roberto Di Matteo admits John Terry's domestic suspension has left his Chelsea side looking vulnerable at the back.
The Blues have missed the reassuring presence of their skipper at the heart of their back four as he serves a four-match ban.
In the three games that Terry has missed, Chelsea have conceded nine goals.
Di Matteo is hoping the defensive gaps can be plugged when he takes his side to Swansea on Saturday and is looking forward to welcoming his captain back into his Premier League plans after that encounter.
"He's obviously been an influential player for us, for sure, and a fantastic defender," said Di Matteo.
"When he plays, he's always played very well for us.
"The other players have done a fantastic job by coming in and playing when they've been in the team but, certainly, JT is a player that we miss.
"The last few games, we've conceded a few more goals than at the start of the season.
"Generally, it's been down probably to a few individual mistakes. But I think our track record is very good and, surely, will continue to be."
He added: "We have to improve but I don't think it's just as simple as that.
"You look at other teams and they're conceding goals, so we certainly have to improve, from the last few games, our defensive organisation."