Just thinking - Klopp wanted to play Lucas as CB because he wanted a passing CB against teams that play deep at Anfield.
So why can't we have Stevie back to play as 4th choice CB with great passing ability? Fitness shouldn't be an issue for a CB. I would love to see him spray passes like a quarterback from defence.
Lucas played there because Lovren and Skrtel are injured, and Kolo is playing on Sunday. Caulker and Illori haven't shown enough to be trusted for such a big game, and Lucas did well against West Ham. It isn't a long term solution.