For the leadoff spot, it comes down to Derek Jeter and Brett Gardner.
Jeter had a down year, let's take a look to see how his numbers compare to Gardner's.
.270, 67 RBIs, .340 OBP, 18 stolen bases and 111 runs scored.
.277, 47 RBIs, .383 OBP, 47 SB, 97 runs scored.
Like I said, Jeter had a bad year, I would count on him having at least a better average and OBP this season. He's working hard in spring training already, and he has something to prove. A similar scenario was in play prior to 2009, and Jeter had a great year.
With that being said, Gardner is improving in virtually all aspects each year. He has only been in the majors since 2008 (playing only 42 games). In 2009, he played in 108 games and in 2010, 150.
Because of this, his numbers have been improving, but at the same time his batting average and OBP have been getting better.
He played in 42 more games in 2010 than in 2009, but he scored 49 more runs, 65 more hits, 14 more doubles, 24 more RBIs, 53 more walks and 21 more stolen bases.
If this doesn't make Gardner's case for the lead-off spot, I don't know what will. Jeter will only drop to second in the order, so I think he will be okay with that.