If you can’t roll your ball on a straight line on a straight putt, you will most likely have trouble being a good green reader.
You need to be able to do three things well in order to putt well.
1. Start ball on straight line
2. Hit the ball at the right speed
3. Be able to predict the line to get the ball started on, based on slope of green. If you can’t get the ball to start on the right line, green reading will be difficult.
This drill works on one component but its a big one.