Even if Johnson does match Damon's production from last year because of a better OBP, a case could be made, that the offensive production the Yankees are getting from plenty of other starters is likely to regress.
Granderson's OPS+ was a dramatic 31 points lower than Matsui's last year. His career average is about 20 points lower than Matsui's. This is very similar to the offensive dropoff from Bay to Cameron which Jacko has described as "massive".
Nick Swisher had easily the best offensive year of his career. There's a good chance he regresses to the norm next year.
Brett Gardner isn't the same hitter as Melky Cabrera. It's hard to know what kind of an offense Gardner will provide over a full season, but his career .256/.325/.352 numbers are not pretty.
Derek Jeter had his best OPS+ since he was 25 years old. The chances of him duplicating that at age 36 are rather slim.
Jorge Posada is a 38 year old catcher coming off shoulder surgery last year. Last he he hit well above his career averages, that's not likely to continue.