Driver says reasons for team's drop may never come to light Mercedes' faltering performance last weekend in Singapore had many Formula One fans and insiders scratching their heads.   Fernando Alonso included.   While the McLaren driver stopped short of mentioning a conspiracy, he did offer his thoughts about the most dominant team of the last two years falling behind the pace.   "We have all been here many years," Alonso said Thursday in the weekly press conference. "And we have never saw (any team) being one second faster all year long and being 1.5 seconds slower for another race.   "This is a mystery that we will probably never understand. But this is F1. You take it or you leave it."   Despite the "mystery" in Singapore, Alonso said he thinks Mercedes will rebound in Japan.   "I think I will be surprised if this (Singapore performance) will be the normal performance of Mercedes."   Mercedes officials said the lack of speed was due to a tire temperature issue.