Chelsea welcome United to west London on Sunday on a run of 10 games without defeat in all competitions, having won nine of those and kept seven clean sheets.
"We are on a very high level, a consistently high level," he said. "I'm not so much into judging if this is the best, but it is very strong.
"We feel very competitive and we feel that we have a good mix of discipline, of structure, but also the freedom and a certain sharpness and a certain grit in our games and performances, which makes us very happy and very competitive."
The German is clear that a team with the talent at their disposal of United can never be discounted, either in a match or the wider Premier League race.
"I will never write anyone off, not in this league and not in this game, because it is a big club, first of all, but it is a very experienced and individually top-level group of players. So this is still the case and part of the performance from us is to not let them perform, because once we let them perform you can see within seconds and within minutes in every game the full potential and the talent of these players, which is on the highest level."
He also doesn't believe you can try and judge whether this is a good time to face Man Utd as they prepare for life under a new manager, and is just looking forward to another tough challenge.
"You can see it either way, in the end we will not lose too many minutes thinking about this, but we will give all our energy and focus on our squad and what we want to do right. We only have one game with Michael Carrick in charge to focus on and to analyse. Of course we have some individual behaviour and some group behaviour that we think we can see as patterns and want to prepare our team for it.
"On the other side it is always the best moment to play against Manchester United because we are up for the big challenges and we want to be out there to play on the highest level, to prove ourselves and to prove a point. We just came from a tough match and there's the next one, this is where we are, where we love to be, and we get challenged on the highest level again on Sunday."
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