Werner would be a great signing. He can play through the middle but is also fast enough, and versatile enough, to cover out wide. If we signed him - and I very much doubt Leipzig would allow it, after losing Keita - I wouldn’t see him as a back up. It would be four players into three positions, plenty of games for everyone, and Klopp could shuffle the pack and keep everyone fresh and firing to take us that step further to a title challenge.
We need more for the front three, as the drop off in level is too great when one isn’t playing. Werner fits the bill, but again, I doubt Leipzig would sell, and if he plays in a very good German side at the World Cup, and does well, which is not hard to imagine, Leipzig will see the price go up and up and the group of possible suitors will grow.