I just installed a Samsung 860 EVO in my mid-2009 MacBook Pro, as a replacement to the HD that crashed. Initially, I thought that the unformatted drive would show up as an option for OS X install and that the install process would take care of it, so I directly replaced the internal HD with the SSD. The SSD did not show as an option for installation. Searched for a solution and found this thread, I did not need to remove the SSD and format it while connected as an external drive; from the install screen I selected Disk Utilities, formatted the drive, quit disk utilities and proceed with the install screen and the drive showed as an option. Thanks for the help.