A player is a player, regardless of how many of them make up a team. A team is a team if there is more than one player per side. You could go with "Side" as a name, but I think you are missing an abstraction here. The scoring for singles or doubles is the same, but slight variations exist in the game play, and the number of players per side. This translates to differences in both logic and data. Sounds like a great case for inheritance.

You need a TennisMatch abstract parent class and two concrete sub classes: SinglesMatch and DoublesMatch.

This gives you the split required to name things as they are. The SinglesMatch has two sides, but only one player per side. The DoublesMatch also has two sides composed of two players each.

Now that we have properly identified the abstractions — this is the key — you can give things proper names: