Wicketkeeper Ben Duckett will miss Northants' pre-season tour of Barbados.
Head coach David Ripley says Duckett, 20, needs to improve his level of fitness.
"Unfortunately he hasn't really found the motivation to reach the targets everyone else has got to," said Ripley.
"We feel it's better that he stays here and works on his fitness. Hopefully he'll respond positively and by the time we return he'll be showing improvement and be back in the group."
Duckett has been part of the set-up at Northants since he was 11. He was previously dropped from the England Under-19 squad for failing a fitness test.
Ripley added: "The leadership team has been really keen to improve standards and the response of the players has been excellent, with so many personal bests on the fitness testing."
Northants leave this week for an 11-day trip to the Caribbean to work on both T20 and 'red-ball' cricket in preparation for the new season.
Left-arm spinner Graeme White, who is nursing a foot injury, is also missing from the tour squad.
South Africans Richard Levi and Rory Kleinveldt will both arrive at Northampton in early April, while Kyle Coetzer remains on ICC World Cup duty with Scotland.
Young all-rounder Saif Zaib, fresh from a successful tour to Dubai with the England Under-17s, and pace bowler Chad Barrett, join the squad for the trip.
"It's disappointing for Graeme who's had a problem with his foot," said Ripley.
"It turns out he has a stress fracture, so he just needs to be off his feet for four weeks.
"In his role as number one spinner he'll have a great opportunity this season and hopefully this injury won't affect that."