Do you really believe a manager would chop and change his team / tactics an hr before kick off for what is a vital game? I certainly don't.
No, and don't the team sheets have to be in before the United game finishes?
The United game shouldn't have any bearing on our preparations. Where it might be a factor is if United lose and we are drawing after 80 mins. Pellegrini's final substitution would probably be defensive rather than attacking.