Sylvain Distin and Niko Kranjcar are keen for more new players to arrive at Portsmouth.
Younes Kaboul sealed a move to Fratton Park on Monday, while Peter Crouch, Glen Little and Ben Sahar have also come in to bolster the squad.
However, Sulley Muntari has left for Inter Milan and Distin feels manager Harry Redknapp will want to venture back out into the transfer market.
Pompey will play in the Uefa Cup this season and Distin believes a bigger squad will be needed to cope with the added workload.
"We do for sure, but we also need a bigger squad to finish seventh, sixth, fifth in the league," said the Frenchman.
"If we sign a few more players we will be a better and stronger team and so then we will have no choice but to try to finish higher and I feel we can do that."
Kranjcar feels the difference between Portsmouth and the established top four of the Premier League is how much they spend on players.
"Money," explained the midfielder. "When you see the top four you see not just the best players in England but also some of the best players in the world.
"One of the main reasons they are able to get them is money - what they can spend in transfer fees and in wages.
"They also have the biggest squads you need to compete successfully in four competitions - that is something the other clubs currently don't have.
"We already have great players in the squad - David James, Sol Campbell, Peter Crouch, all internationals - but we would always welcome more, anything to make the squad stronger."
Crouch and Jermain Defoe are expected to forge a lethal strike partnership over the coming season, even though they drew a blank against Manchester United in the Community Shield.
Defoe remains confident that he and Crouch will be successful together, and feels they could even catch the eye of England boss Fabio Capello.
He said: "We know what we can both do and our record is quite good when you are talking about goals.
"The England manager was at Wembley and I think he knows what we can both do now.
"It is up to the manager but we just need to focus on our club and get off to a good start.
"When the England squad gets selected then I am sure we will be ready."