The rules for how a Competitive Match handles the leaver works as follows:
- If a player leaves before contributing to the match in any way (by dealing damage to opponents or healing allies), then the match cancels automatically. The player who left and triggered the match cancellation will be marked with a loss and penalized appropriately. All remaining players will be returned to the lobby with no impact on their record or skill rating. They will also be given a free opportunity to have a priority requeue.
- If a player leaves a match after contributing to the match, the match will continue, but a two minute timer begins. If the player successfully returns to the match before the timer expires and the match is not over, they will not be penalized and can finish the match. If the player fails to return either within two minutes or the match completes normally, that player will be issued a match loss (regardless of the result of that match) and will be penalized appropriately.
- If in the event the two-minute timer expires, the remaining team members of that match may leave the match without penalty but they will still take a match loss (regardless of the outcome of that match.
All disconnections counts as leaving and will be penalized appropriately. You can learn about Blizzard’s policy here: