Stokes has not played since the end of England’s dismal Ashes defeat. He sustained an adductor injury on the penultimate day of the series in Sydney and was severely hampered.
Stokes was expected to feature along with many England players in the early rounds of the County Championship amid competition for places in the Test XI.
He has been retained as captain despite the 4-1 Ashes loss, while coach Brendon McCullum and managing director Rob Key have also been kept on in their roles.
After those decisions were confirmed this week, Stokes said the past three months have been “the hardest period” of his England captaincy, and backed the current regime to take the team forward.
“He has been training so hard to be ready,” Campbell said.
“He has a lot to prove. You don’t have to be a rocket scientist to know the Ashes didn’t go so well and he is a proud man who wants England to be the best team in the world.
“He, as a professional, is working at getting right and ready to go.”
Campbell also revealed Stokes plans to play for his county in the One-Day Cup this summer.
The 50-over competition is played alongside The Hundred, with counties often fielding second-string sides.
Stokes has not played in the 50-over format since the 2023 World Cup in India and has not featured in the competition for Durham since 2014.
But with Stokes having opted out of The Hundred and not currently in England’s white-ball sides, the One-Day Cup would provide him with some cricket between England’s Test series.
The series against New Zealand ends in late June and a three-Test content against Pakistan begins on 19 August.