3. Thanksgiving 1977, Miami 55 Cardinals 14. Humiliation on national TV, the Cardinals go in with a 6 game win streak, follow it up with 12 straight losses through next season, out of playoffs, loss of coach who goes on to build the best offense in the NFL, and 20 years of (mostly) losing.
This is #1 for me because we were a hot team, were coming off of 3 straight winning season and were among the elite of the NFC, and were in a position to win our 3rd division title in 4 seasons. Then we melt down against Miami on that fateful Thanksgiving game, which, BTW was a tradition being bestowed upon us but when we failed, it was given to the Cowboys. We didn't recover from this loss until 1982 when we began our 3 year winning season run. Anyhoo, this loss was bad enough, then we get bounced by a bad Giants team then lose the final game against the then 1-26 Bucs. We should have been 10-4 at worst that season.
2) 1999-Jets 12 Cards 7: The Jets' only win that season.
3) 1984-Packers 24 Cards 23-Some point to the end of season loss to Washington as a miserable loss, however, we had terrible record in Washington and the 'Skins were a great team then so losing to them in their home park isn't that terrible. Sure the way we lost it was but even worse was this loss. O'Donahue missed an extra point which cost us the game.
4) 2006-Bears 24 Cards 23: The infamous Monday Night game. Here's the deal with this one. We weren't going anywhere that year. We were a developing team but the offense was starting to click with James at RB and Leinart was actually looking good throwing to Fitz and Boldin. Then in come the then undefeated Bears and we were taking them to the shed until Green decided to put the football in his pocket. Now, it isn't losing that made this a miserable game because as I said, we were going nowhere and the Bears were SB bound. No, it was the way we lost. I think you're going to have to look long and hard for a team to have won a game where they score 24 points and only 3 by their offense. Add to that that the Bears offense, and more specifically, Grossman, had 6 turnovers. I can still see James going up the middle for like the 12th time, getting stripped, and Tillman going in for the score. That, to me, was the writing on the wall.
5) 2002-Cards 28 49ers 38-Harken back to this season, Plummers last as a Cardinal. The Cards open the season 4-2 and our 2 losses were good, hard fought games. Then we go into SF and get smoked(yes it was only 10 points but they dominated us all game long). That started a streak where we lost 9 of our last 10(the only win being an OT win against Detroit) which included the 49-0 shellacking by the Chiefs and the game where McNabb lights us up for 4TD on a broken ankle.