Horton was struck in the leg on a hard shot from teammate Dennis Seidenberg and crumpled to the ice. Horton crawled to the bench as play resumed around him and had to be lifted through the bench door by athletic trainer David Zenobi because he could not stand.
Horton was seen limping through the locker room after the game with his left leg wrapped in ice. He was not using crutches and the Panthers initially figured his injury was a deep bruise.
The Panthers did not make a roster move for Saturday's game against the Maple Leafs at BankAtlantic Center because both Nick Tarnasky (knee) and Kenndal McArdle (shoulder) are available.
Horton will not need surgery.
"There's never a good time for this, but especially at this time of year,'' said general manager Randy Sexton.
"This is an opportunity for other guys to step up and show that they belong and carry some of the offensive load. The silver lining is two weeks of Nate's rehab will be done during the Olympic break. It's unfortunate, but it's a fact we have to deal with and move on.''
Sexton and coach Pete DeBoer hope Horton (17 goals, 29 assists) will be back in March;
the Panthers play 10 more games before the two-week Olympic break.
Florida plays its final game before the break on Feb.‚13 and doesn't return until March 2.
David Booth, out since Oct 24 with a concussion, could also return about that time.
The Panthers started the season with a top line of Horton and Booth on the wings with Stephen Weiss at center. With Horton out, Weiss will center Cory Stillman and Michael Frolik for the time being.
"We'll have to get through it without him,'' DeBoer said. "With [Horton] and Booth on the sidelines, we're going to have to be really good defensively.''
Horton is the third Florida player to be injured by his own teammate this season. In November, goalie Tomas Vokoun suffered a badly lacerated ear when he was struck by defenseman Keith Ballard. Later, winger Gregory Campbell suffered a concussion when he and defenseman Bryan Allen collided at full-speed near center ice.
"I hadn't thought about that, but yeah, it's a little odd,'' said Weiss. "That's hockey. Things happen so quickly. If you block a shot from your team or the other team, that can happen.''
Seidenberg felt bad about the accident after Thursday's game and said he apologized to Horton.
"Me shooting the puck at him doesn't make me feel better about the situation, but things happen,'' said Seidenberg, coincidentally the league leader in blocked shots this season with 149.
"I broke his leg, but I didn't mean too. He was in front of me, I was in motion already. It was bad luck. I was trying to get the puck in. It was me trying to make the puck go deep and it would have if Nathan hadn't been there.''