The pair were impressive for last week's Champions League final victory over Manchester City.
Rudiger has been in superb form in the second half of the season and is a regular in the German national team under Joachim Low.
Havertz said, "He has given us so much stability over the last few months. After (manager Thomas) Tuchel's arrival, he played outstandingly.
"As a mentality player, he's also important. On the pitch, he's a warrior. A bit like Kante - you want him in your team.
"Playing against him in training isn't as much fun either. The last few months have been top. It was very hard for him at first and now he's fought his way out of it."
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