The former Celtic keeper pointed to players such as central defender Virgil van Dyke as being important to Southampton’s European ambitions.
“Maybe a couple of players will come in and a couple will go in the summer,” said Forster.
“I don’t think we need a lot to add to the quality that we’ve got.”
Meanwhile, Southampton have confirmed the departure of keeper Kelvin Davis, midfielder Gaston Ramirez and Will Brit, another keeper, after their contracts expired.
Davis, 39, has retired following 10 years at the club, while Uruguay midfielder Ramirez, 25, leaves after a four-year stay, which included a loan spell at promoted Championship club Middlesbrough this season.