GREENBURGH, N.Y. — With a surplus of forwards, the widely expected battle for 13 spots on the Rangers’ opening night roster begins this weekend.

But don’t discount competition “definitely for the 5, 6, 7, 8 spots” on defense, head coach Alain Vigneault said Thursday after 63 players went through their medical testing at the team’s practice facility.

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As of now, the Rangers will have captain Ryan McDonagh, Dan Girardi, Marc Staal, Kevin Klein, Brady Skjei and Dylan McIlrath returning, plus additions Nick Holden and Adam Clendening, as well as prospects, in camp.

Vigneault said veterans Staal and Girardi, who had uncharacteristically poor years, “want to prove they’re ‘d’ players.”

He suggested that a full summer of rest and training — with the Rangers ousted in the first round of the playoffs — may have helped. “They’ve played a lot of games, a lot of big games” in recent years.

“I want to experiment, try different things to see who has chemistry,” Vigneault said and did not rule out the possibility of trades to free any logjams. “We could change some pieces.”

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The Rangers can carry up to 23 players, including two goalies, and Vigneault said he “was not sure” about carrying 14 forwards, hence the possibility of eight defensemen. How much space the Rangers will have under the $73 million salary cap also plays into the equation.