Staal returned Monday for Game 3 against the Washington Capitals but was a surprising scratch for Game 4.
"I wasn't able to go," Staal said. "I'm not gonna go into detail about what happened, but I wasn't able to play."
The 26-year-old Staal, who missed almost half of last season with a concussion, appeared both down and frustrated after participating in the team's optional morning skate at the Verizon Center. The series is tied 2-2.
"It's tough," he said. "You get excited to get into that one [Game 3] and you have to sit and watch the next, so it's certainly not easy."
The loss of Staal is a massive blow to the Rangers' blue line, now missing one of its anchors again -- not to mention that Staal often has been used in a shutdown role against Washington's Alex Ovechkin throughout his career as a Ranger.
It is unclear if Staal will return for this series or at all this postseason.
"With this thing, the way I've been dealing with it is I wake up in the morning and take it from there, so I couldn't speculate one way or the other," he said Friday.
Staal skated the morning of Game 4 but pulled himself out of the lineup before the game.
"On the ice, it didn't go particularly well," he said. "Just, as the day went on, I couldn't, I couldn't see myself getting into a game situation."
Staal played 17:17 over 21 shifts in the Rangers' 4-3 win against the Capitals on Monday and wore a visor in his return. (He wasn't wearing one when he took a shot to the eye from Kimmo Timonen on March 5.) After the game, Staal said he felt "pretty good." His decision not to play Wednesday was not dictated by anything he encountered during Monday's game.
"After the game, it went as I thought it would," he said. "Like I said, nine weeks off [then into] a playoff game isn't easy. You know, what happened in Game 3 and the way I played, it didn't stop me from playing in Game 4, if that's what you're asking."