The England defender believes he has matured as a player and is ready to prove it when the season starts on Sunday.
"I'd say I'm more mature. I've aged. I'm improving all the time and that has been a key factor. Before I didn't play, so it's impossible to put in performances if you don't play," said Johnson.
"Liverpool are one of the big four so they will be in the spotlight a lot more. It could be a big year. We have high hopes within the Liverpool camp."