Saints conceded 60 goals in the Premier League last season, as many as bottom club QPR.
However, the arrival at St Mary's of 24-year-old Croatia international Lovren for a reported fee of £8.5million from Lyon is likely to significantly bolster Pochettino's rearguard.
The Saints boss said: "We're very clear about our goals and Lovren was one of them.
"He is quality as a player, has a presence on the field and he's good at solving difficult situations.
"I think his qualities will really suit the Premier League, so we're very happy to have him and to bring him into this project."
Pochettino continues to be linked with a move for Celtic midfielder Victor Wanyama, and a host of other names are also said to be interesting the South Coast club.
The Argentinian added to the Daily Star Sunday: "There are some rumours of different players joining Southampton and a lot of agents have linked us with players.
"That shows that Southampton is a very professional club, a serious club and an ambitious one.
"It's not just Wanyama that we're looking at. There are a couple more players we are expecting to talk to.
"All the players I have heard mentioned are good footballers and I think they'd all be happy to come here - but perhaps we don't have a place for all of them!"