One of the important new additions to running in Madden 17 is that you can now push a button first to win a tackle battle.
When you are at the main point of impact, the ball carrier can quickly press a button for a better chance at breaking the tackle.
During a tackle where the ball carrier and the defender are in a stand up tackle, you will be able to press a random face button on your controller and win the tackle battle. If you are running, this means you break the tackle. If you are the defender this means you complete the tackle.
The player ratings and size of the players will impact how long you have to push a button and win.