Why would you want a LWF to play LB? This is the usual warping of logic with you.
Generally, more people accept teams need 2 for each position. Then youngsters there after. Its not a rule, of course, but generally accepted logic.
Except here, apparently, where instead of having two LWF, its preferable to have one (that covers CF) and another - if we have to - that is either a kid or a left back. Of course, that makes perfect sense....
Or - look at it this way:
.................wanyama.......
....................DIER
...........winks.........onomah
...........ERIKSEN......ALLI
lamela.............................. ?
MOURA.............................SON
..................llorente
..................KANE
Yep, clear as day, another LWF is definitely not necessary, theres no room for one, what am I thinking?!