#4 Jonathan Tah
The 23 year old centre-back who may be available this summer for Liverpool to go for as he isn't an expensive option and also a very good defender. He is not injury prone like Liverpool's current options after Virgil van Dijk who are Joe Gomez and Joel Matip.
Although Matip had a good season for the Merseyside club, it wouldn't be worth the risk to go into a new season with 2 injury prone defenders and hence his signing could be crucial for Jurgen Klopp's side.
Aerial prowess and tactically aware with the ability to read the game makes him a very desirable centre back for Liverpool. He can also cover for van Dijk if necessary given the Dutchman wasn't rested much last season. With a market value of £36 million, anywhere around £40-45 million could convince the German club to sell him.