When running the 'diskutil list' the blank SSD just comes up as an unnamed, unformatted drive (key is to check it is the correct disk by looking at the capacity ie.
Installed the 'blank' SSD into the MacBook Pro, booted MacBook Pro into Recovery mode and then used Terminal prompt to format the SSD using the diskutil eraseDisk script. In the end, I did what anrah has mentioned above. I also tried it on another notebook running Windows 10, and it was not recognised as a disk on Windows - when i plugged the dock into the Windows notebook, a message came up identifying it as a faulty USB device, but I could not see it as a disk in Disk Management on Windows. Put the new SSD in the dock, connected dock to MacBook Pro, but the SSD was not being recognised at all in Finder or in Disk Utility. The original HDD was still working (but painfully slow), so i had intended to use a SATA III to USB3.0 dock to clone the HDD to the new SSD prior to removing the old HDD and installing the SSD. I had the same issue - bought a new Samsung EVO 860 SSD for my early 2011 MacBook Pro 13 inch running OS X Yosemite.
