Leeds were beaten 1-0 on Saturday night, thanks to Antoine Semenyo's goal just on halftime.
Riemer, standing in for Daniel Farke after he was sent off, said: “Proud of the boys. Unbelievable shift once again, unbelievable performance, created our chances, our moments.
“Disappointed we didn’t score, I think we are playing one of the best teams in the world, we need to also convert one of those chances.
“And then obviously I think we also restricted very few chances considering it is Manchester City.
“This one moment, the worst possible moment just before half-time, they played it also well, so we haven’t been switched on in this one moment.
“As I have said, you play one of the best teams, we are disappointed in each other that we didn’t get something out of this game because we put a really, really great shift once again like this team always does.
“Let’s shake ourselves, recover and make sure we put another shift in against Sunderland and get our points against them.”