With the 9th overall pick in the 2009 draft, and no consensus top pick, not even a consensus top 5, it's possible that nearly any player could slide down to the Packers. The first couple players I'll take a look at are almost certainly not sliding down to number 9, but it's possible. I'll take a look at players from any position, except QB. I can't imagine GM Ted Thompson drafting a top 10 QB.
NFL Draft Scout's top 64 currently has Texas Tech's WR Michael Crabtree as the best player overall. Football's Future (as of 2/2/09), and a couple other mock drafts I've read, have him going to Seattle at number 4. Obviously a 6'3" WR with 4.5 speed is always going to be in demand. It's also good to see that Crabtree wasn't a one year wonder; he had two great collegiate seasons. Ex-Packer WR Robert Ferguson was someone that played only one year in college and it fooled scouts.
Why would the Packers draft another WR? Thompson has drafted a WR in either the 2nd or 3rd round in every draft he's ran; 2005 2nd round WR Terrence Murphy, 2006 2nd round WR Greg Jennings, 2007 3rd round WR James Jones, and 2008 2nd round WR Jordy Nelson. It's not an obvious selection, but it's possible. But if he slips out of the top 5 and down to number 9, there might be a very good reason for it and it's likely he'll keep sliding past the Packers. Although that didn't stop Thompson from drafting QB Aaron Rodgers in 2005 after he slid out of the top 10 and down to the Packers at number 24.