The injury didn't hurt the Rangers in the short term as New York held on for a 2-1 victory over the Philadelphia Flyers on Tuesday night, but it could become troublesome if Callahan is sidelined for any length of time in this already shortened NHL season.
Callahan scored the eventual game-winning goal during a second-period power play and then got hurt in the third during a post-whistle scrum with Philadelphia's Max Talbot, who dragged Callahan to the ice by his arm.
There was no immediate medical update regarding Callahan after the game.
The Rangers managed to kill two late Philadelphia power plays despite Callahan's absence. New York turned aside five of six Flyers advantages, including a 5-on-3 edge in the second period.
"Cally does everything so well -- the little plays, especially blocking shots," said defenseman Michael Del Zotto, who had a goal and an assist. "The guys did a good job of gathering ourselves after he went off with that injury."
The Rangers have largely relied on their top line of Rick Nash, Brad Richards, and Marian Gaborik to provide most of the offense. They sought outside help, and thought veteran Jason Arnott would join the mix, but a failed physical wrecked those plans.
Where secondary scoring will come from now remains to be seen.
Two goals were enough this time, largely because Henrik Lundqvist was sharp in making 26 saves. New York (3-3) has won two in a row for the first time.
Philadelphia (2-5) has dropped two in a row.
Kimmo Timonen ended Lundqvist's shutout bid 7:09 into the third with a power-play goal after the Rangers were caught with too many men on the ice. Philadelphia's power play failed twice in the second half of the period when the Flyers pressed for the tying goal.
"We have to be more hungry," said Flyers forward Danny Briere, who tied a career high with 10 shots. "The 5-on-3 got us. It's something we'll have to look at.
"Their goalie is so good. You need a great shot to beat him."
Ilya Bryzgalov, back in the net after his first game off, was solid in making 26 saves for Philadelphia.
New York got back at the Flyers after losing 2-1 last week in Philadelphia. Last season, the Rangers won all six games over the Flyers.
The Rangers, who have won three of four overall, have one game left on a three-game homestand that ends Thursday against Pittsburgh. New York rallied to beat Toronto 5-2 on Saturday with four goals in the third period.
"We're trying to keep our game consistent," Del Zotto said. "I thought last game we did a great job trying to gain our identity back. We followed up with, maybe it wasn't the prettiest at times, but we found a way to win."
It wasn't easy. With the Rangers short-handed following a penalty for too many men on the ice, Timonen brought the Flyers within 2-1. He was left alone in the high slot when New York had all four players involved in a scrum in the right corner.
The power play for both sides told the story in the second period. Philadelphia was turned away by the Rangers during a 5-on-3 advantage that lasted for 1:17, and then allowed a power-play goal to New York 3:32 after the teams got back to full strength.
Philadelphia had a chance to at least get even after Richards was called for holding, and Derek Stepan took a delay-of-game penalty 43 seconds later.
Flyers coach Peter Laviolette used his lone timeout, but his club got very few pucks to the net despite controlling play throughout. Philadelphia had an added benefit when Jeff Halpern lost his stick in front, but still couldn't create anything.
"We certainly had our chances," Flyers forward Mike Knuble said. "It's the little things. We started to wear them down but couldn't cash in.
"They are great shot-blocking team. We were passing up some good opportunities. The 5-on-3 was a turning point."
The Madison Square Garden crowd let out a roar when Stepan left the penalty box, and then had more reason to cheer when Callahan doubled New York's lead.
The Rangers had scored only twice in 22 power-play chances over their first five games, and failed again on their lone opportunity in the first period. But Del Zotto got involved again to help New York net its second goal.
Nash took a shot from the high slot that Del Zotto tipped in front of Bryzgalov. Callahan got the rebound, calmly settled the puck down as he shifted to his right, and then slid a shot into the open right side at 11:31 for his second goal of the season and 200th NHL point.
The Rangers struck quickly after their top line couldn't get the puck out of its zone during the game's first shift.
New York worked the puck around in the Philadelphia end, and Del Zotto let go a shot from the left point that slid across the ice through a maze of legs and skates and found its way past Bryzgalov, who appeared not to see the puck as Brian Boyle and Benn Ferriero screened him.
The teams will meet three more times, including twice in New York. ... The Flyers are 2-for-27 on the power play in their five losses this season and 3-for-10 in their two wins. They have allowed only one power-play goal in their victories.