If you're wondering why all the Mavs fans on this site find you re ed, this is why.
I'd say he did a decent job "keeping up with" Nash here:
http://www.basketball-reference.com/...804060PHO.html
and here:
http://www.basketball-reference.com/...901090PHO.html
also this was a decent job (I think):
http://www.basketball-reference.com/...904050DAL.html
finally this one wasn't so bad:
http://www.basketball-reference.com/...002170DAL.html
Since they got Kidd, the Mavs are 6-2 against the Suns.
Yeah, just like Devin Harris' defense on Baron Davis changed the 2006-2007 or how his defense on D-Wade changed the 2006 NBA finals. fyi, the Mavs were about to go up 3-0 on Miami with Adrian Griffin starting and guarding Wade until Devin Harris' game changing defense was put on Wade in the 4th quarter. Once Devin The Glove Harris replaced Griffin in the starting lineup, Wade went into beast mode.
I didn't say great, I said semi-decent, there's a difference last I checked. Since Marion was traded, Dirk has played Phoenix 9 times and has had 28 or more points against them all but twice. I didn't feel like averaging it out, but looking at the score, my guess is he averaged well over 30+ points in his most recent 9 games against Phoenix. Marion defended Dirk way better than anyone on Phoenix currently can.