The Englishman left Liverpool on a free transfer last summer at the end of his contract after six years with the club.
"To give you a bit of an insight, I spoke to Jurgen (Klopp) in October of last year and just sat down and had an open conversation," Lallana told BBC Radio 5 Live.
"We have a great relationship and I just said 'what's it looking like for me next year?'. I know I'm out of contract and I know I'm not playing regularly.
"Although I had a pretty big role in the squad around the team, I wanted a bit of honesty. He basically said to me in October, get your agent to start looking for another club.
"That doesn't mean you're not in my plans or he isn't going to use me. Four days later he brought me on at Old Trafford and I scored the equaliser and I think that shows what type of person Jurgen is. He's very honest.
"He said to me I deserve to be playing more and I deserve more game time and to be playing more. He couldn't offer that to me so from then I had his blessing the club's blessing to give my agent the go-ahead to speak to other clubs about next season, which is now this season."