Contradiction with Luke 5:36
This verse contains the same parable as Mark 2:21, so it doesn't directly contradict, but the context differentiates the audience and emphasis in the teaching.
Luke 5:36: And he spake also a parable unto them; No man putteth a piece of a new garment upon an old; if otherwise, then both the new maketh a rent, and the piece that was [taken] out of the new agreeth not with the old.
Contradiction with Matthew 13:52
This verse suggests a harmony between old and new teachings, while Mark 2:21 implies incompatibility.
Matthew 13:52: Then said he unto them, Therefore every scribe [which is] instructed unto the kingdom of heaven is like unto a man [that is] an householder, which bringeth forth out of his treasure [things] new and old.