I agree with the space thing, that's where Moreno is at his best but that has me thinking that it might not so much be a matter if the opposition defends with a low-block or a high line but rather how they attack. So far we've seen Albi selected as the first choice, and he's been great, but all teams we've faced so far have played a system with a lone wingback on his flank. In that sort of system Moreno has the entire flank to eat up and very little risk of an overlapping fullback/winger exploiting him. When it's just a wingback Moreno is expected to seek out and win the ball and there's little risk of him getting exposed or out numbered.
However, if we're playing a four at the back system with winger/fullback combining down the flank, that's when I'm a little more worried about Moreno defensively. I think he's can be like a cat chasing a laser, too willing to seek out the ball rather than hold position, and that allows teams to play around him. It obviously happens less up against a low block defense where the fullback is reluctant to push forward, but a smart fullback is still going to pick his moments IMO. I'd rather not have Moreno in that situation.
So my contention is that teams that attack using A 3-4-3, 4-4-2 diamond or formation where the wide player tucks into midfield, Moreno might be the better options but if they play with genuine wide players and overlapping fullbacks Klopp may select Robertson. Just a theory but my suspicion is Robertson is much better at tracking and handing off an overlapping runner and would be defensively a bit more sound in that sort of situation. I don't think there's a huge difference in the quality of either going forward so I'd be happy with either up against a defense with a low block or high line.
Actually, I know this makes no sense logically, but the opposite is actually true. I'll explain.
In a shape with two players starting on that side of the pitch we would naturally have two players protecting it defensively. Most likely this would be Mane & Moreno. However, with just 1, as you said, just Moreno. In reality though, we usually see Salah watch the LWB and Moreno watch the RWB with Mane pushed forward as a counter threat.
From the oppositions point of view though, when you play with just '1 wide player, the aim to create overloads on that side of the pitch against the 1 defender which is far easier to do than when you have 2 players naturally starting there. Think for example our own formation v Palace. We all agree we play a narrow 3 in both midfield and attack and yet we had 3 or 4 players in almost every attack on the left overloading them. Watch the Arsenal game and you see the same thing. It's AoC vs Moreno, Mane, Firmino & Gini on that flank. AoC even has a pop at Ramsey because he is just letting the overload happen every time.
The difference is that in a system with 2 wide players it is their job to make attacks happen on that side of the pitch and there will e 2 players assigned there to prevent it. You can overload it with more players of course, but that is the starting point. With a 1 wide player system, it is the job of usually him+3 to create overloads with just 1 player specifically assigned to stopping it. This makes the likelihood of success much higher.
The best example of this is Hoffenheim using their 3-1-4-2 formation against us to overload Moreno all night long. Moreno almost entirely ignored the RWB that night and focused on the players there to make the overload. Mane stayed high behind the RWB to counter but did little or nothing to protect him. This was all a clear tactical decision to do so trusting Moreno's ability to defend huge areas of space using his pace. Ballsy but it worked.
