According to Warchant.com, which has Weatherford quotes...I'm just paraphrasing:
QB coach Daryl Dickey told Weatherford that he was sorry and was going to have to make a switch. The score was 24-10 and a Weatherford-led drive ended in a punt.
Lee had been on the headset with Dickey and was warming up when Michael Ray Garvin recovered a fumble and the offense, with Weatherford, went back on the field. Ironically Weatherford led the team to a touchdown and stayed in the game.
During the time before the switch Weatherford asked Dickey what did he need to do differently and Dickey didn't have an answer other than he had to do something to make get the offense a spark.