Love everything about Herrera but I think his high presses are actually a bit stupid because he more often than not loses his man/gets bypassed because he's doing it alone.
I'm not talking about the interceptions or when he's on his back foot (i.e in a 'settled' position and reading the game) or making tackles/blocks. I'm talking about the situations the opposition are trying to bring the ball out and he's gone rushing in trying to put pressure.
His press is uncoordinated with everyone else (tactics, instincts etc) so imo he's actually harming the team because others behind him have to mop up. That's generally 'fine' against the opposition we're playing now but it'd be very risky against good teams. However, having said that, he usually turns it up a notch against the big teams so ermmm I guess it's mostly neutralised.
I'd love to see a proper organised full team press but at the moment, Herrera needs to cut that out of his game if he wants to be more tactically disciplined.
The fact I'm asking so much of him says it all really.
You just described the main reason why the team as a whole functions a lot better when the heart of our midfield, the Pogba-Herrera combo, is supported by an extra midfielder behind them and not ahead of them.
In regards to Herrera, i don't think he'll ever cut the tendency to press the first attacker or to chase the second balls out of his game. It's one of the three things that make him a valuable asset to this team, the other two being his first touch (with which he almost always manages to create space for himself) and his ability to spot potential openings in the final third and offer supporting runs.
Furthermore, it's a rather sensible tactical decision. Firstly, while Mourinho's teams don't use active high pressing often, they try to make the first two or three passes out from the back difficult for the opposition in order to create more time for their defensive transition and regain shape in their half of the pitch. Now, the main options in our attacking trident (minus Mkhitaryan and Lingard) aren't very good at hunting down for the ball. In this sense, the statistics that show Herrera as one of the best players in the league in possession won in the attacking half/final third are indeed very valuable to us. Secondly, Herrera has to press, regardless of the risk of being overran, because our attacks from right include the right winger tucking in and the right back providing width in the final third. So, Herrera basically has to protect two channels when we lose the ball instead of one. In other words, he must try to cut off the pass, otherwise he'll find himself in no man's land with the opponent having time on the ball and options available for a free pass.
Your remarks about the space on Herrera's back which the opposition can exploit is, of course, correct. But to me it seems it's not so much a disciplinary issue for Herrera, whose positional problems occur in the holding role when he has to protect spaces instead of chasing the ball, as it is a tactical "weakness" we have chosen to live with. Another glaring weakness is the inability of our LB to defend 1v1 (at least until Shaw regains full fitness). The first weakness has brought Carrick back into the starting xi and the second has given Rojo (a natural left footed CB who knows what a LB must be aware of too) a second chance in the team.
The other option is to go in full defensive mode, like we did at Anfield, with 10 players constantly behind the ball. But, till now, what we get from Herrera in the midfield (offering Pogba license to roam free in the attacking half included) compensates for the risks we are willing to take in our tactics.
I'll finish as i started and i'll say i really hope that Jose won't change the tactics and he'll keep utilizing Herrera as he currently does. I still believe that they way we attack (recycling possession high up the pitch and working out openings instead of quick attacking transition and players aggressively attacking spaces both on and off the ball) isn't really his cup of tea and i also believe he doesn't feel comfortable without a play maker (#10 or #8) in his team. And since Herrera and Pogba are unmovable in the midfield, i suspect he might look for a #10. Which imho will be the same mistake LvG did when he decided to switch to his favorite 4231 at the start of his second season at United.