Although Eli Manning fizzled in Sunday's playoff loss to the Panthers, the Giants are preparing to exercise an important clause in the second-year quarterback's contract that would keep him with the team through at least the 2009 season. Two people familiar with the Giants' thinking told Newsday that the team is in position to give Manning a $5-million bonus during the offseason, which would trigger a clause that extends the deal to six seasons. The Giants could wait until after next season to exercise the clause, but it's believed they are prepared to do it now. If they do not exercise the clause at all, Manning's deal voids after the 2007 season. If the Giants pay the bonus, they can spread Manning's salary-cap payment over the next four seasons. If they wait until next year, they will have only three years to spread out that bonus. Manning signed a six-year, $45-million deal in 2004 that included $20 million in guaranteed salary. Giants general manager Ernie Accorsi declined comment on the situation. But Andrew Kessler, an associate of Manning's agent, Tom Condon, yesterday confirmed the clause in Manning's contract.