Workstation Player can run virtual machines that other VMware products create.

VMware virtual machines
Workstation Player runs virtual machines that were created by using Workstation 4 and later, GSX Server 3.x, VMware Server, and ESX Server 2.5 and later. Workstation 4 virtual machines run in legacy mode. You must use another VMware product to upgrade virtual machines created in versions earlier than Workstation 4 before you can run them in Workstation Player.