It could be that the husband, being into rugby, has a whole social circle around the sport. His wife, on the other hand, feels left out and lonely. She might not be interested in rugby at all. And when she tries to engage him in other activities or just have some quality time together, he's always preoccupied with rugby - related things, like training, watching matches, or talking about strategies with his teammates.
The rugby - playing husband might be traveling a lot for games. His lonely wife then has to deal with all the household stuff by herself. She may start to resent his absence and the fact that he seems more dedicated to the sport than to their relationship. She could try to communicate her feelings, but he may not fully understand because he's so focused on rugby.