Notice how when making these saves Mamardashvili is about 1 meter or so
in front of the goal line. That shows his great fundamental positioning. By being in front of the line
he makes himself bigger and that is what every goalkeeper should always do. Try and make himself as big as possible given the situation he finds himself in (without risking an easy lob or some sort of other open-netter). That is
the most important goalkeeping skill: positioning. And Mamardashvili has good such movement on many, many occasions. I think that instinctively he has good such movement.
And notice the second Arsenal goal from the yesterday's game. Notice how Kelleher
was disappearing into his own net and thereby making himself
smaller as the cross was coming in. At the moment when the Arsenal player hit the ball with his head one of Kelleher's feet was actually
behind the goal line.
You may think that such things and differences of 1 or 2 meters are not big or relevant. But they very, very much are. Every 10 or 20 centimeters make
an exponential difference in such situations, let alone differences of a meter, or two, or five depending upon the situation.
And during the first Arsenal goal you can notice how Kelleher
did not make one jumping step in front of himself with both feet when Saka turned onto his left foot and it became obvious he would shoot it. By doing that he would make himself bigger. And if you watch Mamardashvili play you can notice that he sometimes and in some situations makes such jumping steps with both feet in front of himself to make himself bigger, close down angles, and give himself the best opportunity to make a save.
This what I have written here
does not mean that Mamardashvili can just like that become a solid number 1 keeper at Liverpool. In my opinion, he can become something like that in about 4-5 years
if he works under (and with) Alisson.