I think 'rubber' refers primarily to a series of games or matches , rather than a single match. It will always be an odd number of matches as a rubber is best of 'x'.
The equivalent in test match cricket is a series, traditionally five matches but they often play fewer nowadays, not always an odd number. One version of bridge is rubber bridge in which you need to win two 'games' to win a rubber (best of three). Several rubbers may be played at one session.
In the Davis Cup if one team is leading 3-0 I would not call the fourth match a dead rubber. At that stage the whole contest is a dead rubber.