Through Yankee fan goggles?
I just gave you the evidence. Mattingly's best 4 years (84-87) accounted for 24.7 WAR. He never exceeded 4 WAR in any other season.
http://www.fangraphs.com/leaders.as...4&ind=0&team=0&rost=0&age=0&filter=&players=0
As you can see, a handful of players can make a solid argument they were better over that four year span. Heck, Mattingly was never better than third highest in WAR in any single year. At least Wright was 2nd one year, behind ARod.
And yes, even Wright's best four year streak (05-08) was better than Mattingly's. The difference being that Wright managed to tack on back-to-back 6+ WAR seasons a couple of seasons after that run.
Mattingly was an excellent player. And if you said, "best hitter in AL for a four year period" or "best at his position for a four year period", then you probably wouldn't have an argument, as Wright couldn't claim that due to ARod. But "best player"? Nope.