The two sides meet next week in the Champions League knockout stages for the second consecutive year and Barca are currently in rampant form with Messi scoring and setting up plenty of goals.
Barca, who are riding an 11-game winning streak in all competitions, defeated City 4-1 on aggregate last season.
“The truth is that we are good,” Messi told Mundo Leo. “Fortunately, after our poor start to the year after our game against Real Sociedad (1-0 defeat on January 4), everything changed for us.
“We are now in a different dynamic and everything is going in the right direction.
“The team has confidence and there is a different attitude and a lot of determination.
“That is the reason why we are today where we are.”
Barca are alive in three competitions.
The Catalan giants have reached the semi-finals of the Copa del Rey and are second in La Liga, just one point adrift of Real Madrid.
“There is still a long way to go,” Messi said. “We have not won anything yet.
“There are still many months left in La Liga and in the Champions League.
“We also have to book our ticket to the Copa del Rey final.
“But we must continue in this way to achieve our aims.”
Barca are attempting to reach the Champions League quarter-finals for the eighth straight season and Messi is aware his side face a huge hurdle in the last 16 of the competition.
Luis Enrique’s side travel to Etihad Stadium on Tuesday before hosting the Premier League outfit on March 18 in the return leg.
“We face City just as we did last year and it’s a team that has a lot of great players,” the 27-year-old said. “It’s going to be a really difficult tie.
“The aim for them is to go through because it has been a while since they last progressed to the quarter-finals.
“We expect a level tie and it will be decided by details.
“It’s going to be a beautiful challenge especially because City have reinforced their team a lot.”
Messi has enjoyed an impressive campaign, scoring 26 goals and setting up 13 more in 23 league appearances.
He is two strikes shy of surpassing his Primera Division goal tally of last season.
The Argentina international has also scored eight times and provided two assists in the Champions League so far.
“The truth is that this season I tried to start it in the best possible way,” Messi said. “I was coming from a disappointing year, where I went through a lot of problems on and off the pitch.
“It was a challenge for me to change the image that I had given in the past season and try to return to be the player I had been in previous years.
“That was my aim and with that motivation I started this season.”