Pep Guardiola believes Manchester City have signed an even better player than they thought in Ruben Dias.

Portugal centre-back Dias has made a superb start to life at the Etihad Stadium since his £64.3million move from Benfica at the end of September.

The 23-year-old has not only proved a strong defender with leadership qualities – as City anticipated – but his levels of fitness and dedication have further marked him out.

City manager Guardiola said: "When you buy players always you have this quality but you never know what is going to happen.

"He is a guy that can play every three days. He recovers immediately and his ability is incredible, as is his understanding of the game.

"He wants to learn and all of us were impressed how he takes care of his body and mind, every day. We were surprised a lot.

"The day after (a game) – 8.30 in the morning in the gym. He makes his routine, he eats perfectly. He lives 24 hours for his profession.

"I can assure you that we signed one incredible player for the next five, six, seven years. That is not easy to find."

Dias has started all bar two of City's last 21 games – both absences coming in a Champions League group stage they made easy work of – since his arrival and formed a strong partnership with John Stones.

It has been an intense schedule but Guardiola feels his reliability has been a key factor in City's recent recovery after a slow start to the season.

Guardiola, whose side host Birmingham in the FA Cup third round on Sunday, said: "The best signs are when as a player you can be used and play every three days. It is not easy to do.

"The quality may always be there but when you have a player who is injured every two or three weeks or every month, and you have to stop every time, that is not good for the team and the club itself.

"That is why we are so fortunate and hopefully he can continue."