Adam Fox of the Rangers leaves the ice after an injury...

Adam Fox of the Rangers leaves the ice after an injury during the third period against the Islanders at UBS Arena on Tuesday. Credit: Jim McIsaac

The Rangers’ chances of beating out the crowded field vying for a playoff spot will be a little bit more challenging now that they will be without top defenseman Adam Fox, who was placed on injured reserve Wednesday with an upper-body injury. Fox will miss at least a week and perhaps more.

A person briefed on Fox’s condition, and speaking on condition of anonymity, said the Jericho native will “be out for a little bit,’’ but expressed confidence that Fox will be back in time to help the Rangers in their quest to make the postseason. The Rangers began Wednesday two points out of the last playoff spot in the Eastern Conference, with 24 games left in the regular season.

Fox was injured in the third period of the Rangers’ 5-1 win over the Islanders at UBS Arena Tuesday, when he fell to the ice while battling with the Isles’ Kyle MacLean and landed on his left shoulder. MacLean fell on top of him, and Fox got up and headed directly to the dressing room, hunched over and clearly favoring the shoulder.

The Rangers finished the game short two defensemen, with K’Andre Miller having left during the second period with what the team called a lower-body injury.

The Rangers called up defenseman Matthew Robertson from AHL Hartford to replace Fox on the 23-man roster. Robertson, their second-round pick in the 2019 NHL draft, has been called up twice before this season, but has strictly served as an extra defenseman and did not dress for any games in either of his prior stints. He has yet to make his NHL debut.

Zac Jones, who has been the seventh defenseman most of the season, will no doubt step into the lineup to replace Fox for Friday's game against the Maple Leafs at the Garden. Jones presumably will take over some of Fox’s duties running the point on the power play.

Should GM Chris Drury want to trade for insurance against the health of Fox, Miller, or any of his other defensemen, the NHL’s trade deadline is March 7.