Have you considered using VMware vCenter Converter Stand Alone edition? https://www.vmware.com/pdf/convsa_50_guide.pdf
According to the users guide you can convert VMware virtual machines from and to Workstation, VMware Player, VMware ACE, VMware Fusion, ESX, ESXi Embedded, ESXi Installable, and VMware Server. You can also import virtual machines from Microsoft Virtual Server and Virtual PC.