No, there is no injured reserve position available in Yahoo! Sports Fantasy Football.
Across all fantasy games, Yahoo! requires a player to be on the real-life DL, IR, IL, etc. in order to qualify for a position there in the fantasy game.
In professional football, if a player is placed on injured reserve, he is deactivated for the season and is not eligible to return. As a result, that player has no fantasy value for the current season.
If a Custom League would like to allow managers to keep IR players for keeper-league purposes, we suggest configuring the league with one extra bench position.