The 25-year-old has started the last eight games and featured in 17 out of 18 overall having returned to Chelsea after a couple of season away on loan in the Premier League.
Lampard said, "He and Fikayo (Tomori) have formed a really nice partnership and it is great to have Andreas (Christensen) back now, and Toni (Rudiger) will be back, because you need numbers in those positions.
"What Kurt has done, which is not easy, is to go out on loan and people then start to consider you something different from a Chelsea player.
"I never did. I told him very early in pre-season that he was part of my plans here and I believe in his qualities. I try to give him that confidence and he has got better and better as the season goes on.
"He is a bit of a leader in the group, strong physically to look at but a quality player, so I am delighted with how he plays."