VMDK is a virtual disk file, what you need is a VMX file. Cruise on over to EasyVMX and have it create one for you, then just replace the VMDK file it gives you with the Cnrome OS one.
EasyVMX is good since VMWare Player has no VM creation stuff in it (at least in version 2, not sure about 3). You had to use one of VMWare's other products to do that.