I can answer that with two words: "Dave Campo".
The darkest period in Cowboys history was 2000-2002.
Still......
You don't lose to an expansion team in their first ever regular season game, no matter the coach, no matter the GM, no matter the makeup of the team's roster.
Emmitt Smith, Darren Woodsen, Dexter Coakley, LaRoi Glover, Greg Ellis, Dat Nguyen, and Roy Williams were on that team. All were Pro Bowlers at least once in their careers.
That one loss against the Houston Texans is the most embarrassing and humiliating moment in Cowboys franchise history.
For the sake of .....the Cowboys running game averaged 6.5 yards a carry. The Cowboys beat the Texans in total yardage.
The Texans even had two more penalties than the 9 the Cowboys had. The Cowboys defense sacked the Texans twice as many times.
The very first play in the Texans history was a 43 yard penalty for pass interference on Cowboys CB Bryant Westbrook, a six year veteran and former 1st round #5 overall draft pick. The Texans scored a TD on their first ever offensive drive. The Texans very first defensive effort was a three and out on the Dallas Cowboys. This is how the game started.
The Texans second and third defensive effort in their franchise history also ended three and out. Three consecutive three and out for the Cowboys to begin the game against an expansion team playing their very first regular season game in franchise history. Five Super Bowl championships barely wipes away the stench from that miserable game.
A book was actually written detailing that specific game. Thank all the gods they didn't turn it into a musical comedy.