Antonio Conte has admitted he is worried about the severity of Cristian Romero's hamstring injury as Tottenham wait for the latest scan results.
Romero has already established himself as Spurs' best centre back and looks set to play a major role in his manager's back three formation, but an injury suffered on international duty with Argentina has put him on the sidelines for an undetermined period of time.
Ahead of Tottenham's Europa Conference League fixture with NS Mura, Conte said: "We're waiting for another scan. Honestly, I think his injury is serious, I don't know now the time he needs to recover.
"We have to wait for the next scan and then the doctor can give more information on the dates for his recovery.
"I am not thinking about [signing another defender in] January because there is still a long way to go, we have many games to play and also I want to make my evaluations about the squad and players.
"Now I am very focused on the present as the present for me is very important. I need to make many evaluations about the whole squad and then we will see what happens."
Conte has confirmed there will be rotation in other positions, with Ryan Sessegnon set to feature at left wing back.
He added: "All the players available will come with us and they must be ready to play. I need to make rotation because there are players that are a bit tired because they played many games with the national team and also we worked a lot in the last two weeks."
Spurs will be without Giovani Lo Celso in Slovenia, while young striker Dane Scarlett also won't feature. The Europa Conference League is probably Tottenham's best chance of winning silverware this season and Conte admitted they are targeting improvement and success.
"We want to build something important and try and lift trophies together, this must be our target," the former Inter and Chelsea boss said.
"In England it is not easy because the other teams are very, very strong but I know we can improve a lot. If you ask me how much time we need before it happens, it is very difficult to tell you this. In our heart and mind, this must be our inspiration and we are to try to do this for the best of the club.
"I have found a group of players that want to work and improve and this is a good place for me. I can arrive at any club and I want to bring my ideas but if you don't have the ability of the players it is impossible. I have seen positive things at Tottenham and have felt good vibes. This is a good place to start."