Explain to me why Michy shouldn't start? He's been great throughout the pre-season and there's no reason why £58m Morata would just walk straight into the XI. Right choice, IMO. Striker position desperately needs competition and the total amount of goals Michy+Alvaro score is more important than what they individually score.
On the other hand, I expected to see Musonda instead of Boga. I guess it also comes down to attitude, defensive contribution etc. and not just technical ability, which I think is where Musonda excels at.