Major League Baseball is adding some new features to their annual home run derby event this year. To start, they are competing by league with designated captains choosing each side. American League captain David Ortiz is joined by Adrian Gonzalez, Robinson Cano, and Jose Bautista. National League captain Prince Fielder chose Rickie Weeks, Matt Holliday, and Matt Kemp to help him represent the Senior Circuit.

Players will be competing to be the overall winner as well. The rules for that part of the competiton are the same as previous years:

All participants get 10 outs per round, with the four players with the most homers advancing to a second round. The two players with the highest cumulative number of long balls after the second round advance to the Championship Round, where first- and second-round homers do not carry over.

MLB has also introduced a social media wrinkle to this year’s competition. Several participating players (Bautista, Ortiz, and Kemp) will be tweeting throughout. They will be joined by other All-Stars in attendance who will be watching from the sidelines (Heath Bell, Justin Upton, Hunter Pence, and several others). Follow below for an updating stream of the All-Stars tweets throughout the event.