First of all it is third match, which means calculations get matter. It is time to think about next stage, safe energy, safe players. For Spain draw is enough to go further. Only if lose by more than two goals and Iran draws against Portugal, the Furia Roja has to travel home which is so unlikely.
Diego Costa is the man, so clinical, doesn't need many opportunities or space to find a net. He plays simple football, never skill gifted but know how to harm. So far he attempt 2.5 shots in International stage, in local league takes average 1.7 shots and 2.4 in Champions League. Why bookies support him with double total today? Morocco ain't that poor like Panama or Saudi Arabia, they won't to stay behind a lines, and will try to score.
In favor I think there would be the possibility that he will be substituted like in recent two encounters with Portugal 55' & Iran in 89'. Since Spain needs only draw here there might be less tension and pressure in the match.