Malcolm Jenkins has been in the league for a dozen years, and no one ever got him comfortable playing quarters coverage.
Jenkins has always been more comfortable playing near the line of scrimmage and using his instincts to be around the ball or cover man-to-man. He could drop deep and make some plays, but that has never been his game. He lacked the patience to sit back in a zone, keep his eyes in the right places, and not be overly aggressive. A small mistake in space can lead to a significant gain. No one was ever really able to get Jenkins out of his comfort zone, take the illustrations out of the playbook, and make it all make sense in a way that worked for him.
Then he met Aaron Glenn.