Please take a look at http://www.vmware.com/pdf/VirtualDiskManager.pdf where you can find the command line options as well as a sample command (page 10) which converts a virtual disk into an ESXi compatible format and stores the target .vmdk directly on the ESXi host.
I don't use a MAC, but I think thisis the same for VMware Workstation as well as Fusion.
André
