Happened last year in my league. In week 14, the first week of playoffs in my league, Guy A was losing to Guy B by quite a lot going into Monday night's game between New Orleans and Atlanta. Guy B had no players left. Guy A, who was behind, still had Brees to go. Brees had a good game and his final completion of the night, with only a 2-3 minutes left in the 4th quarter, gave Guy A a 0.99 point lead over the other team. Obviously Guy A was going nuts and calling people saying how he pulled out the miracle win. Well, unfortunately for Guy A Atlanta got the ball back at the end of the game, couldn't do anything with it, and turned the ball back over to New Orleans. On the very last play of the game Brees came in and took a knee. In Yahoo leagues that counts as -1 yard rushing or -0.1 points. Guy A ended up losing and being knocked out of the playoffs by 0.01 points.
To make matters worse, turns out he would have won the league championship had he won that game. Doh!