Despite finishing second in the Premier League last year, just two points behind champions Manchester City, Liverpool conceded 51 goals in all competitions and Rodgers says improvement is needed across the board.
“(Defence) is a place where we want to be better, there’s no doubt about that,” he told Sky Sports News.
“It wasn’t good enough to concede that many goals, considering the amount of possession we had and amount of goals we scored.
“Generally of course the whole team will be looking to improve, and there are areas that we will specifically be looking at between now and August.”
Liverpool are back in Champions League action for the first time since the 2009/10 season and Rodgers credits their return to Europe's top table for aiding his recruitment drive.
“We’re in the Champions League, players want to come here and play and that’s great,” he said.
“It is easier to attract players but you’ve still got to do your work and convince players to come. The off-season wasn’t much of a holiday really! The scouting team, myself, the directors were flying all over Europe to get players in."
After the sale of Luis Suarez to Barcelona for £75m after this year’s World Cup, Liverpool have welcomed England star Adam Lallana from Southampton, as well as Emre Can and Lazar Markovic from the continent.
And Rodgers is hopeful of further arrivals before kick-off in August.
“At this level you have to be able to spend and the owners have been great,” he added.
“They’ve backed us in terms of getting players in and hopefully we can get one or two more in which will give us great depth going into all the competitions.”
“The best players want to play at the best level.”
Southampton defender Dejan Lovren is one reported Reds target but Martin Skrtel has welcomed potential competition at the back.
"We need a big squad because there will be more games, there might be some injuries," Skrtel said.
"We've signed a few players and maybe a few more will be on the way. We'll all try to fight for our places and competition is only good, it pushes you."