That would be a weird trade for the Mavs. They are loaded on the wings and thin at center. Why would they want to make the situation even worse?
Another report came out late yesterday from the Mavericks denying that they had any interest in a sign and trade with Miami, and/or in general, involving Brendan Haywood.
So there appears to be nothing to this.
Just Miami inquiring about Haywood's availability and then being rejected.