It's been clear to me, since the PL started getting more and more competitive that having pace in your attack is probably the most important thing when thinking offensively. This is especially true on the flanks when you deploy two wide attackers, as seems to be the norm with most top teams. For me pace comes in two parts: speed and acceleration. I have never been a huge Lukaku fan and this isn't a thread against him, or Sanchez or anyone but I would bet we have one of the slowest accelerating front threes in the league. Our starting team has been a Sanchez-Lukaku-Mata front three before for example. These aren't players who can take people on or go past a man regularly - this is crucial playing the way we do because to threaten the opposition whe you sit deep you need both out balls (impossible without pace) and the ability to counter (impossible without pace). Lukaku is quite fast once he gets going but was easily marshalled by Alderweireld/Vertonghen who are relatively average pace-wise because he's so big and heavy his acceleration is probably the same as theirs, if not slower. We actually have a rapid front three of Rashford-Martial-Lingard if we were to try and use it. All three are fast, Rashford incredibly so and all three have great stop start acceleration, especially Martial with the ball at his feet. Mourinho has nothing to lose and must have been sick of Lukaku missing chances and touches last night and how poor Alexis looks in general. Why not try the young guys out, teams will have to sit deeper to account for their pace at the very least.