I don't think the Rams make it back to the superbowl in 2001 if Vermeil stays.
That Chiefs team had a top offense and lost in the first round of the playoffs. The only playoff game they played. The defense failed them in that game in a high scoring game against the Colts and Peyton Manning. The defense needed an overhaul but Vermeil stayed with this guys because he is so loyal.
The Chiefs in subsequent seasons continued to have problems on defense and never made it to the playoffs again. Martz tore up the defense in 2001 and it went from near the bottom to #1 in the conference in 2001. The Rams returned to the playoffs in 2000, 2001, 2003, 2004.
