Ive noted the similarities between Barry and Rodri before - however the difference here is not the players (though there are some differences - Barry was even more complete in the dark arts of winning free kicks for instance) - the difference is the team they are playing in
Barry had 4 very good defenders behind him whose main purpose was to defend -with Rodri he has two fullbacks flying forward all the time - leaving space behind them - one of them cant defend either (Barry had Zabba, Clichy and even Sagna (I think) who were all competent defenders not to mention Kompany, Lescott (who was a very basic defender but he could defend)
Our style of play is a lot more exposed than it was under Mancini -thats not a criticism of either styles as both had success and produced great football (peps football is much more attractive to watch but Mancini's was pretty good to)
Thats why Rodri is more exposed - teams also play differently against us now...when we won the title with Mancini, teams would try and play against us - now the vast majority sit back and just hit us with pace on the break - thats why the liverpools, utd and Wolves (last season) all did us over...leicester this season already - some teams have the players to exploit us (Mane, Salah, Vardy Rashford, Greenwood, and most of Wolves front line as well) - the lieks of Burnley dont
This maybe why Pep has started with Both Rodri and Ferna in his games so far - it fell apart when ferna was taken off vs Leicester (but in the interst of fairness Wolves could/should have scored 2-3 against us as well)
now with Dias this might change - he is front foot defender...he will try and stop those counters before they happen - ths will at times lead to mistakes, yellow cards (Maybe even red) but this may also push the back line further forward and compress that huge gapping gap between our midfield two and back line - the only issue is the bal over the top and into the channels behind our fullbacks...with walker thats not such an issue (though its not perfect) but on our left hand side mendy gets caught in two minds all the time and gets exposed...he then also doesnt get back quick enough when we lose possession - this is why teams target our left side..they know its easy to expose him
If we are in for a elft back (though we may not get one) Pep et al. have clearly lost a bit of faith in mendy.