Former Hampshire player Berg is to undergo minor surgery after suffering a slight hernia in pre-season training at the County Ground.
Berg will not be flying with the rest of the squad for their pre-season training camp in Singapore on Monday, and he will be joined in staying home soil by four-day captain Rossington.
The County's red ball skipper is not injured, but is missing the trip for family reasons.
The injury to Berg is a blow to the player, who joined Northants at the back end of last season and has signed a two-year deal with the club, as well as Ripley, who sees the experienced 39-year-old as a key man for the upcoming Specsavers County Championship Division One campaign.
But the head coach is hopeful the injury is just a minor setback, and he expects the South African-born player to be available for selection sooner rather than later.
"Gareth picked up the injury this week," revealed Ripley.
"He has a little hernia injury, while Luke Procter has picked up a side injury as well, but he is still going to Singapore.
"With Gareth, it is likely he is going to have a small operation, which is disappointing because he is in great shape.
"He has trained very hard, and then right at the end of the winter he has felt a little bit of discomfort.
"It's not great timing, and it is disappointing, but it is a long season and the injury to him and Luke might just affect the first game or two, but hopefully after that we will be back to full numbers."
Northants will be in Singapore until March 20, before returning home for pre-season workouts at Derbyshire and Nottinghamshire..
Their first game at the County Ground is on April 13, when they take on Leeds Bradford MCCU in a first-class fixture, before their opening Championship match of the season against Warwickshire at Edgbaston on April 19.