It doesn't matter if they have 50 days rest afterwards, I never get why people say that. What matters is how much energy they have to give after the city match, and the answer is: not 100%. Some will be more affected than others but it's madness to expect no changes, and it would be madness to implement no changes. As someone said above, I'd be happy to see the full backs changed as well as studge and origi starting, also because against an obdurate Sunderland they could be very useful outlets in an attacking sense.
It'll be interesting to see the team Klopp puts out, either way. By hook or by crook, 3 points would be incredible today and would put Chelsea under just a smidge extra pressure Vs Spurs.