"The main reason is I still think I'm young enough to play football and I know chances to play here would be limited. I spoke to the manager and I didn't want him to make promises about how many games I would play, but this season has been mentally very difficult. I haven't played a lot and playing is what I enjoy most," the legend told the club's official website.
"I understand it isn't possible to play enough games here for me to be happy, so I had to look elsewhere. I got the option to go abroad to Bayer Leverkusen. The whole package was good, they have big plans for me and hopefully I can go there and help them to be successful."
When asked about returning to Anfield one day as a coach he added: "Coaching is something which has always been in my mind, but I have to take my badges first. At the end of my playing career I will look to take the badges and then see. I would like to come back here one day as a coach."