One of the things that makes some players more successful than others is that they use as much mana as possible. Every second you spend with a full mana bar results in permanently lost mana. If you never let your mana bar get full, you should theoretically earn 1600 mana over the course of a 3m30s match (100 starting mana + 900 for the first 2m30s + 600 for the last minute).
So a great stat to display at the end of the match would be how much mana each player actually SPENT. This could easily replace the current mana stat, which doesn't really provide any useful information.
Skilled players are going to see very similar numbers, but this information might be very eye opening for less experienced players.