Issue with Smalling is, as a defender he's decent, can do a good marking job on a top player and do well. That's fine playing the likes of City and Liverpool. His problem is when we play teams who sit back. Even in our current poor situation, many teams will park the bus against us. In these types of games his lack of composure on the ball is highlighted. Ole obviously wants to play more from the back, as does Southgate for England and Smalling doesn't fit that system. No-one saying he's a bad player, he's not. In fact I'd of liked to have kept him for certain games, but at this stage of his career he needs to be playing regular football, and he won't get that with us.
This is what i mean about buzz words. I don't mean to pick on you but I see this all the time in here. If you play teams that just sit back and let you have the ball, they wont press as high as teams that want the ball, so "playing out from the back" becomes a moot point in this context. These buzz word arguments often leads to this self-contradiction in here.
You want your team to be able to play out from the back when teams press high, so you don't quickly lose the ball and gives up attacking momentum. The whole team need to be able to play quick passes, if they are to transition their possession into a quick attack, or they need to be able to make the other team drop deeper some how, and then recirculate the ball to keep possession until the attacking shape has been establish. Defenders who pass the ball well can act as midfielders, to then break the team down. This is true. But is that it? Is all you need a couple of defenders who fit the criteria for this and it's good? No. While it definitely is about getting a team to play a certain way, you need to strike a balance around the whole team to make success of this modern formula. If you have attackers who don't know when to play it risky, and when to keep possession you'll lose the ball more than the system requires and this will have a direct effect on the tasks asked from the defenders. If you don't have the ball, how is it going to help to have a playmaker, if him and the people around him can't win the ball? This is why Pep is making it a rule all his players has to be good at winning the ball back, it is not enough to just be good when you have it, you have to go get it. This is what will keep your attacking momentum, not just their ability when they have the ball.
And the same balance that has to be struck with defenders in this context too.
If the team build an attack with Smalling, however slow, they'll eventually get there. Maybe the chance for a quick counter is gone, but you can establish an attacking shape. Maybe he won't play a penetrative pass, or maybe you'll have a De Bruyne to do that. Regardless, If the attackers lose the ball, or it gets cleared, you want your defender to be able to play his part in winning it back quickly from his positioning in a high line. If he does, then he has contributed to keeping you're attacking shape. You can continue your attack without dropping your whole team deeper. This is something Smalling does well, and it has great value to this setup. Remember the games in EL where we dominated possession? Big reason for that was Smalling's ability to win the ball back and keeping it in the team. Lindelof is Smalling's replacement, and every game I see how totally winnable duels isn't even attempted by him and it causes our whole team to drop deep, to protect our defensive shape. It is good to defend in numbers, but the amount of times we have to do it each games is ridiculous. Up and down, up and down, and it is not all due to Lindelof of course.
To summarise with a single point I will say this. While being good on the ball certainly is a factor in using possession to your advantage, an even bigger factor in keeping possession is actually winning the ball back, and the easiest way to strike a balance is to have players of high levels with different qualities that all get what is asked of them.
The question shouldn't be if a player fit one criteria, but rather be evaluated on overall usefulness. If you do, you certainly don't end up trusting Jones, Rojo and Bailly,.On the topic of Smalling, I think he has proven himself as both a reliable and versatile player performing at good levels in different set ups, so I don't understand why his contribution, willingness to adapt and professionalism has been underplayed to the point he wanted to leave.
In a less than a perfect team, which will always be the case, a defenders most important job is to defend, if he does that well he is worth consideration in any setup. Because he'll always find himself in those situations where he'll save your ass. If he has other qualities that can be used like speed, strength to contribute in attack, it is up to the manager to utilise those strengths to the benefit of the team.
You could argue Smalling doesn't fit the "modern" formulas, but does Pogba? Do Rashford fit? McTominay? DDG? In certain areas, they do, but in others they clearly don't. The same as Smalling. It is about the balance, rather than just one thing.