Drafting players who were friends or colleagues as juniors is often a good way to build team bonds. Mateships are groups of players who share some affinity. Collecting all the players to Complete level in each Mateship group earns a Milestone reward. Some Mateships are easier to achieve than others!
The most common Mateship is through a shared trait; some based on the type of nickname they are called, others on how they all have a particular play style, or a common personality quirk. Some mateships are based on on-field positions, and others on being highly- or lowly-rated in an attribute.
Mateships can also be collected of players from the same region, boasting the same star rating, or some other connection indicated by the title of the Milestone.