Penguins coach Mike Johnston said Letang was evaluated at the hospital and will remain there overnight.
"I just went to make sure I got a piece of him so he couldn't jump by me and he obviously went into the boards awkward," Doan said after the game. "You never ever want to see anyone like that, especially a guy with his caliber and everything he's went through in the past couple years."
The hit that injured Letang can be seen below:
Letang suffered a stroke last year and has a history with concussions. The 27-year-old has scored 11 goals and has 43 assists this season for Pittsburgh.
In January, Letang missed one game after being hit by Flyers forward Zac Rinaldo during a game. Rinaldo was suspended eight games.
The Penguins host the San Jose Sharks on Sunday.
- Molly Geary