BOSTON — Three days after the United States women’s hockey team lost to Canada, 5-1, in an exhibition game here on Oct. 25, USA Hockey unexpectedly added Cayla Barnes, an 18-year-old freshman at Boston College, to its roster.

The move may just be insurance for the coming Four Nations Cup, which begins Tuesday outside Tampa, Fla., and is the last major women’s hockey tournament before the 2018 Winter Olympics.

Or inserting Barnes, a prodigious defender who has won three consecutive under-18 world championships, into the lineup could be a shrewd psychological and tactical ploy.

After all, Barnes is one of the few players on the American team who is somewhat unknown to Canada.

Her addition is one example of the chess-like maneuvering within the most intense rivalry in women’s hockey. By mid-December, the two teams will have played up to eight games against each other — including one on Wednesday — in the span of two months, plotting their final moves of a four-year buildup to an expected meeting in the gold medal game in Gangneung, South Korea, on Feb. 22.