DENVER - Trouble on the horizon? Rick Nash might not be available when the Rangers face the Avalanche on Friday night and the Coyotes in Arizona on Saturday night.

Nash, who is considered day-to-day, left practice abruptly Thursday when his back "locked up" while shooting and later walked slowly out of the building.

"I just threw it out. I couldn't move," Nash said after receiving treatment at the University of Denver's Magness Arena. "I've had locked-up backs, but the last 21/2 years, I've been pretty good that way. I just have to put my trust in the trainers . . . and get it to keep moving. I felt good out there for the first three drills and then it twisted the wrong way when I took a shot, and it kind of went out on me."

"He's day-to-day, I don't know about [Friday]," coach Alain Vigneault said. "These things can turn around quickly or sometimes they linger for a couple days.

"Two years ago he missed three days or something, but I don't know if it's the exact same thing."

Nash, who has a goal and five assists in 12 games, said he would receive more treatment at the team's hotel to "hopefully get it moving and loosened up. We'll see how I feel in the morning."

Emerson Etem likely would step in on a line with Derick Brassard and Mats Zuccarello if Nash cannot play, Vigneault said. Etem, who was acquired from the Ducks for Carl Hagelin in the summer, was a scorer in juniors, but that production hasn't translated to the NHL.

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"Probably when he came into the league he was pegged to be a more offensive player," Vigneault said. "If you want those guys to succeed, you've got to put them in roles that they can succeed in. That might be a better-suited place for him."

Etem has one assist in three games this season.

If Etem dresses, three lines will have changed since the 5-2 win over the Capitals on Tuesday night. J.T. Miller was moved at practice from the fourth line to the second with Derek Stepan and Chris Kreider, and Jesper Fast was dropped to the fourth with Dom Moore and Jarret Stoll.

Nash's absence also would affect the penalty kill and power play. Kreider was added to the first power-play unit with Ryan McDonagh, Brassard, Stepan and Zuccarello.

Notes & quotes: It appears that defenseman Dan Boyle could be a healthy scratch for the third time this season in favor of rookie Dylan McIlrath. "I might consider giving him one of these days off," Vigneault said. "Obviously, the player's not thrilled with that." In speaking with Boyle last week, Vigneault said: "I told him, I've got to look at the big picture. We've got a back-to-back here." . . . Henrik Lundqvist will start against the Avalanche (4-7-1), which played Thursday night in Arizona. Antti Raanta could make his third start Saturday night.