Liverpool boss Jurgen Klopp is confident he can keep his back four together.
Virgil Van Dijk and Joel Matip are aged 27, Andrew Robertson 25 and Trent Alexander-Arnold 20 - and the manager insists they are only going to get better.
“The best way would be we don't have to do a lot (in the transfer market) because the age group of the players is brilliant," Klopp said.
“They all have a long career ahead which is cool and how it looks at the moment is that they want to spend the majority of their careers here which is cool as well.
“Having different characters always helps, if you are all mainstream, all the same way, that it difficult. It is just nice to see.
“It is not important how much you cost or how big the price was. Virgil came here and it was a big step for him.
“He knew he could improve, he wants to improve, he was at Celtic and could win titles there, but this is the first club really where.... He sees his future here now. “It was exactly the same for Robbo. It is not important if you are £7million, £8million, £10million. Joel was the same and he was on a free transfer.
“Trent dreamed of nothing else since he was born of being involved in something like this and that is all good. It is all different ideas and different characters. Joe (Gomez) is the same and he's finally fit again as well.
“It is probably not the most expensive defence in the world but it is a proper one, a really proper one. Wherever good players are coming from, wherever they are raised, wherever the dream started, they are welcome here at Liverpool.
“Now it feels to me like we have a proper bunch of players together, not only the defence. They really stick to each other and the club is in a way which is exceptional. They want to do the job 100%."